New_ CDMA Material (LT)v

Prepared by:

Course OutlinesIntroduction to mobile communicationCDMA network architectureCDMA network interfacesCDMA principlesTransmission problemsCDMA air interfaceCDMA key technologies CDMA Traffic Cases

Introduction to Mobile Communication

Why communication systemscommunication systems structureTerminalsNetwork Transmission media Why wirelessHistory of wireless communicationIntroduction to mobile systems Multiple Access TechniquesWireless ChallengesCellular System Concepts

Why communication systems

What is communication systems

why communication systems

Examples of communication systems

Communication system architecture

Structure of communication systems

Terminals (televisions , radios, phones ,..etc)

Networks (television networks , PSTN , mobile networks .etc)

Transmission media

Why Wireless?sourceDestinationTransmission medium

Why Wireless? (cont.)The kinds of transmission medium :

1- Twisted-pair: It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable: It is greater bandwidth than twisted-pair but it is very expensive.

3- optical fibers: It is very high bandwidth , very high bit rate and inherently transmission medium.

Why Wireless? (cont.)Although, On a wired transmission link (copper or fiber optic), the characteristics of the medium are very well controlled and easily predicted

It still fixed and limit the mobility of the user

While the wireless (Radio) telecommunication bridged the distances between people who wish to Communicate while they move.

So, we will use the radio waves to transmit and receive.

But first we need to know the properties of these waves.

History of wireless communication18381866 Telegraphy: Morse perfects his system; Stein hill finds that the earth can be used for a current path; commercial service is initiated

1864 Maxwells equations predict electromagnetic radiation.

18871907 Wireless telegraphy : Heinrich Hertz verifies Maxwells theory. Demonstrations by Marconi and Popov; Marconi patents complete wireless telegraph system (1897). 19231938 Television: Mechanical image-formation system demonstrated; DuMont and others perfect vacuum cathode-ray tubes; field tests and experimental broadcasting begin.

1936 Armstrongs paper states the case of frequency modulation (FM) radio.

1937 Alec Reeves conceives pulse code modulation (PCM).

19381945 Radar and microwave systems developed during World War II; FM used extensively for military communications.

1962 Satellite communication begins with Telstar I.

History of wireless communication (cont.)19681969 Digitalization of telephone network begins.

19701975 PCM standards developed by CCITT.

19751985 High-capacity optical systems developed; the breakthrough of optical technology and fully integrated switching systems.

19801985 The first generation of modern cellular mobile networks put into service. But it was all based on analog system:1981 NMT-450 in Northern Europe1983 AMPS in the United States.1985 TACS in Europe and China

Introduction to mobile systems What is mobile systems

Difference between mobile systems and PSTN

The first generation of modern cellular mobile networks ( based on analog system)1981 NMT-450 in Northern Europe1983 AMPS in the United States.1985 TACS in Europe and China

Introduction to mobile systems (2G)

1985 Standardization for second generation digital cellular systems is initialized.

1992 GSM900 in World Wide.

1993 GSM1800 in Europe.

1994 GSM1900 was firstly commercial.

Global System for Mobile (GSM) is a second-generation digital cellular telephone system. GSM became the world's leading and fastest growing mobile standard, spanning over 174 countries, serving more than one in ten of the world's population.

Difference between 1G and 2G mobile networks The main difference between 1G networks and 2G networks is1 G systems was analog but 2 G systems was digital

The analog mobile systems have main restrictions of:the limited capacity, voice-only services high operational cost. different systems are incompatible in terms of equipment and operation, e.g NMT and TACS.

Difference between 1G and 2G mobile networksCapacityWhile with digital systems such as GSM, the available frequency spectrum is used more efficiently, leading to increased capacity reductions in associated costs for network operators, equipment suppliers and subscribers.

ServicesAnalog mobile systems were originally designed for voicedigital mobile systems can support voice, data and a range of additional services such as:a short message service call forwarding ISDN compatible.

Introduction to mobile systems (2.5G)GSM offers circuit-switched with good voice quality, but it is providing data rates of 9.6 kbps which is too slow.

In 1999 General Packet Radio Service (GPRS) reuses the existing GSM infrastructure to provide higher data rate

It was lunched to increase the data rate to 115 kbps by:using the packet-switched in data transmission Defining new coding scheme.

In 2001 Evolved Data rate for GSM Evolution (EDGE) offers data rate of 384 kbps by using new modulation scheme(8psk)

Introduction to mobile systems (North America)In 1993 Code Division Multiple Access (CDMA) is a second-generation digital cellular telephone system that was first deployed. CDMAOne describes a complete wireless system based on the TIA/EIA IS-95 CDMA standard, including IS-95A and IS-95B revisions. IS 95A provides data rate up to 9.6Kbps/14.4KbpsIS 95B Provides data rate up to 115.2Kbps IS 95B is categorized as 2.5 G

CDMAOne provides a family of related services including cellular and fixed wireless (wireless local loop).

3G Systems

In 2000 the ITU-T was responsible for the IMT-2000 specification, which is meant to be a guideline for every 3G standard

Universal Mobile Telecommunication Service (UMTS) is the marketing name for the 3G has two standardization bodies: 1- 3GPP which uses the W-CDMA technology. 2- 3GPP2 which uses the CDMA2000 technology.

WCDMA as a 3G ApproachThe 3G solution for GSM is called WCDMA (Wideband CDMA). WCDMA requires a new radio spectrum as it operates in ultra wide 5-MHz radio channels.

WCDMA meets the IMT-2000 requirements of 384 kbps outdoors and 2 Mbps indoors.

The earliest deployment was by NTT DoCoMo.

CDMA2000 as a 3G ApproachCDMA2000 represents a family of technologies that includes:CDMA2000 1X CDMA2000 1XEV.CDMA2000 1X can double the voice capacity of CDMAOne networks and delivers peak packet data speeds of 307 kbps in mobile environments. CDMA2000 1xEV includes: CDMA2000 1xEV-DO delivers peak data speeds of 2.4Mbps and supports applications such as MP3 transfers and video conferencingCDMA2000 1xEV-DV provides integrated voice and simultaneous high-speed packet data multimedia services at speeds of up to 3.09 Mbps.

3G Systems & IMT2000 Greater than 2 Mbps User Data Rate 10 Different Frequency Bands CDMA Low Power (PSD) Results in: Low Detection Probability Less Susceptible to Jamming

Migration to 3G

Multiple Access Techniques

But how will we use this radio frequencies to serve all users.

Meaning of multiple access techniques

Benefits of multiple access techniques

Why we must use multiple techniques

Multiple Access TechniquesFrequencyFrequency Division Multiple Access (FDMA)

Multiple Access TechniquesTime Division Multiple Access (TDMA)

Multiple Access TechniquesCode Division Multiple Access (CDMA).

FDMA, TDMA, vs CDMA

Wireless ChallengesTo provide coverage for a large service area of a mobile network we have two Options:

Install one transceiver with high radio power at the center of the service area

Drawbacks: The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area So, Powerful transmitters & huge equipment are required. The usage of the radio resources would be limited, So, Capacity is limited to the frequency band allocated.

Wireless Challenges (B) Divide the service area into smaller areas (cells)Advantages: Each cell as well as the mobile handsets will have relatively small power transceivers. The frequency spectrum might be reused in two far separated cells. This yields: 1- Unlimited capacity of the system. 2- Good interference characteristics

So, The solution is going to Cellular Systems

Cellular System Concepts

The Area to be covered is divided into small cells.So,Low Transmission power.Smaller equipment size.Capacity of the system can be increased, Ex.: In the figure: Capacity of one big cell = Capacity of the band Capacity of cellular design = 7 * Capacity of one big cell.

Cellular System Concepts Frequency reuseReuse Pattern(Cluster):

Cells are grouped into ClustersAvailable Band is distributed among the cells of the clusterEach frequency is reused after the same distance DReuse Plan:(D/R)= 3NN is the number of cells in a cluster .Where R is the cell radius

For more efficient use of available spectrum and hence enhancing the system capacity ,each cell is divided into three sectors of 120o

In each sector a directional antenna is used whose narrow beams allow reusing the channels more often

Sectorization is suitable to use in dense urban areas Cellular System Concepts Sectorization

Directional AntennaCellular System Concepts Sectorization

Omni AntennaCellular System Concepts Omni Sector

Definition of Coverage Areas

CDMA2000 1x network

The Base Transceiver Station (BTS):Consists of the radio transmitters, receivers and the antenna system required to provide the coverage area for one cell.

Records and passes to the BSC the Signal strength measurements

Converts the CDMA radio signals into a format that can be recognized by the BSC.

Channel coding and interleaving

Spreading and despreading

Realization of diversity

Demodulation

The Base Station Controller (BSC) Manages the Radio Communication with the mobile station over the air interface.

Supervises the transmission network and the operation of each BTS

The BSC is the central node within a BSS and co-ordinates the actions of Base Stations. (i.e. The BSC controls a major part of the radio network)

BTS configuration: This involves the allocation of codes to channel combinations and power levels for each cell according to available equipment.

Cell Description Data (e.g. cell identity, maximum and minimum output powers in the cell).

control the power control process

The Base Station Controller (BSC)Handling of MS connections :

During Call Set UpPaging:Signaling set-upAssignment of traffic channel

During a Call:Dynamic power control in MS and BTSLocating

The Mobile Services Switching Center (MSC)The primary node in a CDMA network is the MSC. It is the node, which controls calls both to MSs and from MSs. The primary functions of an MSC include the following:

Administers its Base Station Controllers BSC(s).Switches calls to/from mobile subscribers.Records charging and accounting detailsProvides the gateway functionality to other networks.Service provisioning.Control of connected BSCs.Provides the gateway functionality to other networks.

Gateway Mobile Switching Center (GMSC):

Gateway functionality enables an MSC to interrogate a HLR in order to route a mobile terminating call. It is not used in calls from MSs to any terminal other than another MS.

For example, if a person connected to the PSTN wants to make a call to a CDMA mobile subscriber, then the PSTN exchange will access the CDMA network by first connecting the call to a GMSC

Home Location Register (HLR):The HLR is a centralized network database that stores and manages all mobile subscriptions belonging to a specific operator.

It acts as a permanent store for a persons subscription information until that subscription is cancelled.

The primary functions of the HLR include: Stores for each mobile subscriber:Basic subscriber categories.Supplementary services.Current location.Allowed/barred services.Authentication data. Subscription database management Controls the routing of mobile terminated calls and SMS.

Visitor Location Register (VLR):The role of a VLR in a CDMA network is to act as a temporary storage location for subscription information for MSs, which are within a particular MSC service area.

Thus, there is one VLR for each MSC service area. This means that the MSC does not have to contact the HLR (which may be located in another country) every time the subscriber uses a service or changes its status.

The VLR may be integrated with the MSC.

For the duration when the MS is within one MSC service area, then the VLR contains a complete copy of the necessary subscription details, including the following information: Identity numbers for the subscriber Supplementary service information (e.g. Does the subscriber has call waiting activated or not)Activity of MS (e.g. idle or busy)Current Location Area of MS

Short Message Center (MC or SC)As an independent entity in the CDMA cellular mobile communication system

the short message center works in coordination with other entities such as MSC and HLR

Functions of SMC to implement the reception, storing and transfer of the short messages from CDMA cellular mobile communication system subscribers, and store subscriber-related short message data.Manages the resend of the SMS

1x Packet Data ServiceCompared with IS-95, in order for the CDMA2000 user data service to access, the CDMA2000-1X core network should be added with:

PDSN, HA (providing Mobile IP service) AAA; these three functional entities are the cdma2000-1X access network should be added with PCF functional entity.

These new devices are required by the packet data service transmission to provide high-speed access to the Internet, videophone, and e-commerce to the users in the 3G mobile communication system.

System Architecture R-P Interface, A10/A11

AAAHAPDSNFirewallBSC/PCFBTSBilling System

As a access gateway , PDSN(packet data service node) provides the CDMA2000 mobile station with services for Internet access or Intranet access.PDSN acts as an interface between Radio Network and Packet Data Network.Provides the mobile station with Simple IP access service or Mobile IP access service.In Simple IP, PDSN acts as a Network access server, while in Mobile IP, PDSN acts as Foreign Agent(FA) for Mobile Station.At the CDMA2000 1x stage, the maximum access rate available for each subscriber is 153.6kbps PDSN acts as a client of AAA server.PDSN

AAA authenticates the script file information of the subscribers, authorizes data services, and Collects accounting information from PDSN, completes accounting.

Authentication simple IP and mobile IP.

Authorization subscriber configuration information.

Accounting collecting billing data(both radio specific and IP network specific) for each packet data call. AAA

Simple IP Access

- Similar to the network access through dialing-up modem on the fixed telephone . - Assigning dynamic IP addresses and accomplishing the data communication with MS as the calling party .Mobile IP Access - Providing a route mechanism in the internet. Assigning MS fixed addresses to connect any sub-networks - Accomplishing the data communication with MS as the calling party or the called party, and holding data communication when MS handoff between different PPP link.

Access Method

Parameters InvolvedIn a CDMA system, the following parameters are defined to identify a user and his location:MIN/IMSI MDN ESN SID/NID LAI

MIN/IMSIMobile subscriber identity/international mobile subscriber identityFor example, 0907550001/460030907550001Not more than 15 digits3 digits2 digitsIMSIMCCMNCMSINNMSI

MDNCC+MAC+H0H1H2H3+ABCDInternational mobile subscriber DNNational valid mobile subscriber number Mobile directory numberFor example, 8613307550001

ESNA unique Electronic Serial Number (ESN) is used to identify single MS. An ESN includes 32 bits and has the following structure:

31......24 23......18 17......0 bitManufacturers number retained equipment SNFor example, FD 03 78 0A (the 10th Motorola 378 mobile phone)The equipment serial number is allocated by a manufacturer.

SID/NIDMSCID (Exchange Identity)= System Identity (SID) + Exchange number (SWIN)is used to represent a certain set of equipment in an NSS network. For example, Unicom CDMA Shenzhen MSC is labeled as 3755+01

LAIPAGING message is broadcast within a local area, the size of which depends on traffic, paging bearer capability, signaling flow , etc.Format: MCC+MNC+LACMCC: Mobile Country Code, 3 digits. For example, China is 460.MNC: Mobile Network Code, 2 digits. For example, the MNC of Unicom is 03.LAC: Location Area Code, a 2-byte-long hexadecimal BCD code. 0000 cannot be used with FFFE.For example, 460030100LAI = Location Area Identity

CDMA interface techniquesWhat is interface

Functions of interfaces

Why we need such technologies To provide a high-speed, low delay multiplexing and switching network to any type of user traffic, such as voice support, data,or video applications

Examples for switching techniques used ATMSS7

What is ATM?ATM for Telecommunications is Asynchronous Transfer Mode, (not Automatic Teller Machine!).ATM is a technology that has transport, switching, network management, and customer services built into it right from the start.In general, ATM means that traffic is carried in small, fixed-length packets called cells.A technology that integrates advantages of circuit switch and packet switch.ATM can support any type of user services, such as voice, data, or video service.

ATM Overview53byte fixed length cell= 5Bytes cell header+48Bytes payload.ATM must set up virtual connection before communication.ATM network will confer with terminal on parameter of QoS before the connection is set up.Contract5-Bytes Header48-Bytes Payload

ATMs AdvantageIntegration of various services such as voice, image, video, data and multimedia.Standardization of network structures and components. This results in cost savings for network providers.Transmission that is independent of the medium used PDH, SDH, SONET and other media can be used to transport ATM cells.ATM is scaleable, i.e. the bandwidth can be adapted extremely flexibly to meet user requirements.Guaranteed transmission quality to match the service required by the user (quality of service, QoS).

Connectionless & Connection-orientedConnectionless: Every packet is transferred from different routes, so the receiving order of packets doesnt possibly depend on the sending order.Connection-oriented : All packets are transferred from the same route , so the receiving order of packets depends on the sending order. Time delay is fixed.

Traditional Switch Models Characteristic- Circuit Switching Data is sent from the same route, so time delay is fixed High-speed switching Fixed rate- Packet Switching Support multi-rate switching Take full advantage of bandwidth/waste of bandwidth Time delay is not fixed

ATM Cell

ATM CellGFC ( Generic Flow Control): It is intended for control of a possible bus system at the user interface and is not used at the moment.

VPI ( Virtual Path Identifier): The VPI contains the second part of the addressing instructions and is of higher priority than the VCI.

VCI ( Virtual Channel Identifier): VCI in each case indicates a path section between switching centers or between the switching center and the subscriber.

PTI ( Payload Type Identifier): Indicates the type of data in the information field.

CLP ( Cell Loss Priority): Determines whether a cell can be preferentially deleted or not in the case of a transmission bottleneck.

HEC ( Header Error Control): Provided in order to control and, to some extent, correct errors in the header data that may occur. The HEC is used to synchronize the receiver to the start of the cell.

VP and VCWhy two fields?think VPI as a bundle of virtual channels. (256 VPI on one link)the individual virtual channels have unique VCIs. The VCI values may be reused in each virtual path.

ATM Virtual ConnectionUNI cell VPI =1 VCI =1UNI cell VPI =20 VCI =30NNI cell VPI =26 VCI =44NNI cell VPI =6 VCI =44NNI cell VPI =2 VCI =44123

123132231ATM Virtual Connection

AB

Features of ATM Connection oriented Fast packet switching Statistical multiplexer Supports voice, data and video service Provides QoS

ATM Sublayer ModelATM Protocol Stack ModelOSI Reference Model UserPMDTCPHYATMAALCSSARInterface management7 Application 6 Presentation5 Session 4 Transport 3 Network 2 Data link 1 Physical

Two sublayers:

Transmission Convergence Sublayer (TC)transmission frame generation/recoveryProcessing HECcell delimitingtransmission frame adaptation

Physical Medium Dependent Sublayer (PMD)Link coding Network physical mediumFunction of ATM Physical LayerAALATMPHY

Cell switch Quality of Service Processing the cell header Types of payload Multiplexing /Demultiplexing of different connection cellFunction of ATM LayerAALATMPHY

Support services for user Segment and reassemble Complete the change between User-PDU and ATM payloadFunction of AAL layerAALATMPHY

Function of ATM AAL OverviewFunction of ATM AAL:Provide a high-speed, low delay multiplexing and switching network to support any type of user service, such as voice, data,or video applications.ATM PayloadConstantBit RateData BurstsVariable Bit RateATM Cell MultiplexingAAL SDU

TCP/IP ProcessApp DataTCP HeaderTCP headerApp DataIP HeaderIP HeaderTCP HeaderApp DataLLCSAR-SDU#1SAR-SDU#2SAR-SDU#3SAR-PDU#4SAR-PDU#5TCPIPSNAP/LLCAAL5CSSARATMPHYCell header will be added to SAR-PDU, whose VPI and VCI depends on the map table of IP address to PVC/SVC. Then ,the cells will be sent to Physical Layer. Perform the transmission of ATM cells via physical media.LLCIP HeaderTCP HeaderApp DataPADCPCS-PDU Tail

INARP in IPOAPVC ModeATM NetworkPVC Any IPOA terminal that wants to communicate with other terminal must know the destination IP address. But how to know the IP address? PVC connecting the source and destination terminals should be set up first. For example: Terminal A must set up a PVC to B in order to know the IP address of B.

Network InterfacesMain interfaces1- Um interface (air interface)It is defined as the communication interface between MS and BTSIt is physical linking is realized through radio link

2- A interfaceIt is defined as the communication Interface between NSS and BSS (MSC and BSC)It is physical liking is realized using standard 2.04 Mbit/s (E1) PCM digital transmission link

Network InterfacesNetwork subsystem Interface1- B interface:It is defined between VLR ad MSCIt is used by MSC to ask VLR for information about the location of MS, or to update MS location2- C interfaceIt is defined between HLR and MSCIt is used for route selection and management information (billing)

Network InterfacesNetwork subsystem Interface3- D interfaceIt is defined between HLR and VLRIt is used for exchanging the information about MS location and Subscriber managementThe VLR is integrated with MSC and HLR is integrated with AC. So, the physical linking of D-interface is realizing through the standard 2.048 Mbits/s4 - E interfaceIt is defined as the interface among different MSCs of controlling adjacent areas [Handoff]it is physical linking is realized through the standard 2.048 Mbits/s PCM digital transmission link.

Multiple Access TechnologiesFDMABased on codes, all users obtain traffic channels at the same time and on the same frequency band, for example, WCDMA and CDMA2000Traffic channels on different frequency bands are allocated to different users,for example, AMPS and TACSTraffic channels at different points of time are allocated to different users, for example, DAMPS and GSM

Advantages of CDMAAdvantages of CDMA The coverage radius is 2 times of standard GSM.

Coverage of 1000 km2: GSM needs 200 BTS's, while CDMA requires only 50.

Under the same coverage conditions, the number of BTS 's is greatly decreased

Simple project design & convenient capacity expansionGSM: N=4 Frequency reuseSimple Network PlanningCDMA: N=1Frequency reuse

Green HandsetLow transmission power: Accurate power control, handoff control, voice activation

Systems

Mean transmission power

Max transmission power

GSM

125 mW

2W

CDMA

2 mW

200mW

High Quality Voice(1)

CDMA principles

CDMA PrincipalsThe core idea that makes CDMA possible was first explained by Claude Shannon, a Bell Labs research mathematician

Shannon's work relates amount of information carried, channel bandwidth, signal-to-noise-ratio, and detection error probabilityIt shows the theoretical upper limit attainable

In 1948 Claude Shannon published his landmark paper on information theory, A Mathematical Theory of Communication.

He observed that "the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point." His paper so clearly established the foundations of information theory that his framework and terminology are standard today.

CDMA Principals

SHANNONS CAPACITY EQUATION

C = Bw log2 [ 1 + S/N ]

Bw = bandwidth of the signal in HertzC = channel capacity in bits/secondS = signal powerN = noise power

Spread SpectrumBy a small amount of analysis in Shannon equation we can see that the: bandwidth of the signal (Bw) is inversely proportional to the signal power

This result can be used to serve more than one user by the same frequency in the same time by generating a new dimension to discriminate between the different users and make the spreading process So, the question is how to make the spreading process

Two Types of Spread SpectrumDirect Sequencenarrowband input from a user is coded (spread) by a user-unique broadband code, then transmittedbroadband signal is received; receiver knows, applies users code, recovers users dataDirect Sequence Spread Spectrum (DSSS) CDMA IS the method used in IS-95 commercial systems

DSSS Spreading: Time-Domain ViewAt Originating Site:Input A: Users Data @ 19,200 bits/secondInput B: Walsh Code #23@ 1.2288 McpsOutput: Spread spectrum signal

via air interfaceAt Destination Site:Input A: Received spread spectrum signalInput B: Walsh Code #23 @ 1.2288 McpsOutput: Users Data @ 19,200 bits/second just as originally sent

DSSS Spreading: Frequency-Domain ViewThe improvement of time-domain information rate means that the bandwidth of spectrum-domain information is spread.The Y-coordinate is energy density.

Spread SpectrumProcessing Gain (CDMA Spreading Gain)

Processing gain is the ratio of a spreading rate to a data rate.

Consider a user with a 9600 bps vocoder talking on a CDMA signal 1,228,800 Hz wide.

So, the processing gain is 1,228,800/9600 = 128.

The processing gain in IS-95 system is 128, about 21dB.

The processing gain is calculated as follows: 10 x log10128 = 21db

Spread SpectrumPrinciple of Using Multiple CodesUsing several multiple codes improves the system because they are independent

Advantages of Spread Spectrum

Give the ability of multiple access

Avoid interference arising from jamming signal or multi-path effects.

Covert operation:Difficult to detect

Achieve Privacy: Difficult to demodulate, (Noise like signal.)

Impossible to Eavesdrops on the signal expect using the same code

DefinitionsForward link: the direction from a base station to a mobile stationReverse link: the direction from a mobile station to a base station

CDMA channel: Code Channels are characterized (made unique) by mathematical codes (stream of 1s and 0s)

Walsh Code64 Sequences, each 64 chips longA chip is a binary digit (0 or 1)Each Walsh Code is Orthogonal to all other Walsh CodesThis means that it is possible to recognize and therefore extract a particular Walsh code from a mixture of other Walsh codes which are filtered out in the processIn forward direction, each symbol is spread with Walsh code Walsh code is used to distinguish the user in forward linkFor IS95A/B, in the reverse, every 6 symbols correspond to one Walsh code. For example, if the symbol input is 110011,the output after spreading is W5164 (110011=51).For CDMA2000, in the reverse, Walsh function is used to define the type of channel (RC 3-9)

Walsh Code How to generate Walsh code? Its simple to generate the codes, or theyre small enough to use from ROM

Wim represents ith (row) Walsh function of length m.

For example, W24 is 0101 in the Matrix W4

Walsh CodeTwo same-length binary strings are orthogonal if the result of XORing them has the same number of 0s as 1s

M- sequenceIn CDMA system, user information is encrypted by means of scrambling. The scramble code used here is M-sequence. Shown in the figure is an M-sequence generator made up of a shifting register sequence with certain feed bake. The period of the output sequence is 2N-1 (N being the number of shifting registers). That is to say, the shifting register sequence resumes to the initial status when every 2N-1 pieces of codes are output.

Short codeThe short code is a binary M-sequence with 15 shift register. Short code is PN sequence with period of 215 - 1 chipsSequence with different time offsets are used to distinguish different sectors Minimum PN sequence offset used is 64 chips, that is to say, 512 PN offsets are available to identify the CDMA sectors (215 /64=512). the two sequences scramble the information on the I and Q phase channels

Long codeThe long code is a PN sequence with a period of 242-1 chipsEach mobile station uses a unique User Long Code Sequence generated by:Long Code State Register makes long code at system reference timing, to the 42-bit A Mask Register holds a user-specific unique pattern of bits (32-bit ESN+10-bit for operator) Each clock pulse drives the Long Code State Register to its next stateState register and Mask register contents are added in the SummerSummer contents are modulo-2 added to produce just a single bit output The output bits are the Long Code, but shifted to the users unique offsetGenerated at 1.2288 Mcps, this sequence requires 41 days, 10 hours, 12 minutes and 19.4 seconds to complete.

Long code

Coding Process on CDMA Forward Channels

Effects on Radio CommunicationSignal degradation can be classified by type :Path Loss during distance covered by the radio signal, it is called Free space path loss , it can be calculated by LFS = 32.44 + 20 log F (MHz) +20 log d (Km)Signal attenuation Resulting from shadowing effects introduced by the obstacles between transmitter and receiver Fading of the signal Caused by numerous effects all of which are related to the Radio propagation phenomenon

Effects on Radio Communicationthe Radio propagation phenomenon ReflectionPropagating wave impinges on an object which is large compared to wavelengthE.g., the surface of the Earth, buildings, walls, etc.DiffractionRadio path between transmitter and receiver obstructed by surface with sharp irregular edgeWaves bend around the obstacle, even when LOS does not existScatteringObjects smaller than the wavelength of the propagating waveE.g., foliage, street signs, lamp posts

Fading ProblemsShadowing (Normal fading): The reason for shadowing is the presence of obstacles like large hills or buildings in the path between the site and the mobile. The signal strength received fluctuates around a mean value while changing the mobile position resulting in undesirable beats in the speech signal. Rayleigh Fading (Multi-path Fading):The received signal is coming from different paths due to a series of reflection on many obstacles. The difference in paths leads to a difference in paths of the received components.

Effects on Radio Communication

Fading Problems

Fading Problems Solutions

Increase the fading Margin

Fading Problems Solutions

Antenna diversity (Space Diversity)The cell transceiver will use two receiving antennas instead of one. They will be separated by a distance of about (10* ), and they will receive radio signals independently, so they will be affected differently by the fading dips and the better signal received will then be selected.

Fading Problems SolutionsSpace diversityThat means we can use two antennas for receiving instead of one antenna to avoid the fading of the signal at a certain receiving point

The RAKE ReceiversTo avoid the multi-path effect there are several RAKE Receivers in the mobile station and the base station where the signals which arrives at mobile station at different time will be demodulated separately and will be given a different time delay so as to keep them in phase and the Mobile station will perform vector adding of these signals

d1d2tttd3transmissionreceivingRaker combinationnoiseRake Receiver

The Principle of RAKE ReceiverThe RAKE technology can overcome the multi-path fading and enhance the receive performance of the system.

CDMA air interfaceWhat is air interface

Defines the technology between MS and BTS

Carries most of the characteristics of the mobile systems features

Determines the capacity and quality of the system

RNP and RNO depends mainly on air interface parameters

CDMA frequency assignment

Band Class

uplinkMHz

DownlinkMHz

0

824849

869894

1

18501910

19301990

2

872915

917960

3

832870

887925

4

17501780

18401870

5

412460

420493

6

19201980

21102170

7

746764

776794

5

CDMA frequency assignmentThere are 8 band classes stipulated in the IS-2000 for the working frequency band of the CDMA2000:

1. Band Class0: Corresponding to the North America cellular frequency band, also in use in China, Hong Kong, Australia, North Korea and Taiwan.2. Band Class1: Corresponding to the PCS frequency band in North America.3. Band Class2: Corresponding to the TACS frequency band.4. Band Class3: Corresponding to the JTACS frequency band.5. Band Class4: Corresponding to the PCS frequency band in South Korea.6. Band Class5: Corresponding to the NMT-450 frequency band. (Nordic Mobile Telephone)7. Band Class6: Corresponding to the IMT-2000 frequency band.8. Band Class7: Corresponding to the 700MHz cellular frequency band in North America.

General CDMA System ModelInformation stream (transmission)InterleavingSource decodingdeinterleavingSource codingInterleavingdeinterleavingScramblingUnscramblingSpreadingDespreadingModulationDemodulationRadio frequency transmitting Radio frequency receive Information stream (reception) channel codingchannel decoding

Analog to Digital converter

In CDMA system the signal is sampled by 8KHZ (or 8 K sample per second) with each sample using 13 bits with linear quantization, which gives an input data rate of 104 Kbps.

Then it is broken into 20ms frames.

But because the air resource in a wireless system is very precious, a more effective coding mode is needed to use a rate as low as possible in the case where voice quality is guaranteed which is the function of source coding.

Source CodingSource Coding in CDMA is done by Vocodervocoder is such a device the main principles of it are to extract some voice feature parameters when a person speaks and transmit these feature parameters to the peer party. Then, the peer party will recover the voice with these parameters based on the promise between the two parties.Meanwhile, the codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with:speech activity total bit error rate.

Source CodingWhere this Vocoder has two rates: 8K QCELP (Rate Set 1: 9600, 4800, 2400 and 120 bps) 13K QCELP (Rate Set 2: 14400, 7200, 3600 and 1800 bps)The third voice code is the Extended Variable Rate Coder (EVRC) which has a full rate output of 8Kbps in QCELP but has voce quality very closer to the 13Kbps in QCELP

Channel EncodingConvolutional code or TURBO code is used while a channel is encodedConstraint length = shift register number+1.Encoding efficiency = the input bits number / the output symbols number.Convolutional encoder

Interleaving The direction of the data stream It can be seen from the figure that the data are read row by row into an interleaver at the transmit end, read column by column out (this process is called interleaving) and propagated after other modulation process. Then, the data enter the interleaver at the receive end row by row and are read out column by column (this process is called de-interleaving)

SpreadingThe forward channel is channelized by a Walsh code and the reverse channel by a long code.In the reverse, every 6 bits from the encoder output corresponds to one Walsh code.That is to say, every 6 symbols are spread into 64 chips.In the forward, each bit from the encoder output corresponds to a Walsh code.That is to say,each symbol is spread into 64 chips.

Modulation The forward channel modulated by means of QPSK.

The reverse channel by means of OQPSK can reduce the fluctuation range of modulated signals.

For OQPSK As opposed to the data modulated by I pilot PN sequence, the data modulated by Q pilot PN sequence has the delay of half a PN chip (406.901ns).

Thus, the maximum phase change of four-phase modulation is 90 degrees instead of 180-degree mutation.

Modulation-QPSK1.2288Mcps: the PN chip rate of the system.After being spread, all the forward channels in the same carrier are modulated by means of QPSK (OQPSK in the reverse), converted into simulation signals and transmitted after clustering.

Channel structure in IS-95A

Introduction to channels

Forward and reverse channels

Types of channels (physical , logical)

Types of Channel in IS-95AForward channel Forward Pilot Channel Forward Sync Channel Forward Paging Channel Forward Traffic Channel (including power control subchannel)

Reverse channel Access Channel Reverse Traffic Channel

Pilot ChannelUsed by the mobile station for initial system acquisitionTransmitted constantly by the base stationThe same Short PN sequences are shared by all base stationsEach base station is differentiated by a phase offset of 64 bitsProvides tracking of:Timing referencePhase referenceSeparation by phase provides for extremely high reuse within one CDMA channel frequencyAcquisition by mobile stations by using :Short duration of Pilot PN sequenceUuencoded nature of pilot signalFacilitates mobile station-assisted handoffsUsed to identify handoff candidatesKey factor in performing soft handoffs

Pilot Channel GenerationThe Walsh function zero spreading sequence is applied to the Pilot

The use of short PN sequence offsets allows for up to 512 (215/64) distinct Pilots per CDMA channel ( frequency carrier)

The PN offset index value (0-511 inclusive) for a given pilot PN sequence is multiplied by 64 to determine the actual offsetExample: 15 (offset index) x 64 = 960 PN chipsResult: The start of the pilot PN sequence will be delayed 960 chips x 0.8138 microseconds per chip = 781.25 microsecond

Pilot Channel Acquisition procedureWhat is pilot acquisition

Pilot Channel Acquisition procedureThe mobile station starts generating the I and Q PN short sequences by itself and correlating them with the received composite signal at every possible offset.In less than 15 seconds (typically 2 to 4 seconds) all possibilities (32,768) are checked.The mobile station remembers the offsets for which it gets the best correlation (where the Eb/N0 is the best.)The mobile station locks on the best pilot (at the offset that results in the best Eb/N0 ), and identifies the pattern for defining the start of the short sequencesNow the mobile station is ready to start de-correlating the SYNCH channel with a Walsh code.

Sync ChannelUsed to provide essential system parametersIt used Walsh function number 32Used during system acquisition stageBit rate is 1200 bpsSimplifies the acquisition of the Sync Channel once the Pilot Channel has been acquiredMobile Station re-synchronizes at the end of every callNow the mobile enters the idle state

Sync. Message Parameters

System ID (SID) 16-bit unsigned integer identifying the system

Network ID (NID) 16-bit unsigned integer identifying the network within the system (defined by the owner of the SID)

Pilot PN Sequence Offset Index (PILOT_PN) Set to the pilot PN offset for the base station (in units of 64 chips), assigned by the network planner

Long Code State (LC_STATE) Provides the mobile station with the base station long code state at the time given by the SYS_TIME field, generated dynamically

Sync. Message Parameters

System Time (SYS_TIME) GPS system-wide time as 320 ms after the end of the last superframe containing any part of this message, minus the pilot PN offset, in units of 80 ms, generated dynamically

Paging Channel Data Rate (PRAT) The data rate of the paging channel for this system, determined by the network planner00 if 9600 bps01 if 4800 bps

CDMA Frequency Assignment (CDMA_FREQ)

Sync Channel Generation

Paging ChannelsThe Paging Channel uses Walsh function 1

Two rates are supported: 9600 and 4800 bps

The paging channel message:System parameters messageAccess parameters messageNeighbors list messageCDMA channels list message

The functions of a paging channel: Paging mobile stations and responding access channels Assigning traffic channel

Paging Channels Generation

CDMA Forward Traffic Channel

Used for the transmission of user and signaling information to a specific mobile station during a call.

Maximum number of traffic channels: 64 minus one Pilot channel, one Sync channel, and 1 - 7 Paging channel.This leaves each CDMA frequency with at least 55 traffic channels.Unused paging channels can provide up to 6 additional channels.

Now we will talk about the generation of the traffic channel procedure in details

Forward Traffic Channel 8 kb Vocoding GenerationWalshfunctionPowerControlBit I PN9600 bps4800 bps2400 bps1200 bps(Vocoder)ConvolutionalEncoding andRepetition1.2288 McpsLong PN CodeGeneration800 HzR =1/2,K=9 Q PNDecimatorDecimatorUser Address Mask(ESN-based) 19.2ksps1.2288 McpsScramblingbitssymbolschips19.2kspsCHANNEL ELEMENTMUXBlockInterleaving

Rate 1/2, k=9 Convolutional EncodingSymbols generated as the information bits transit through the encoder, are related to all the bits currently in the register.Each information bit contributes to multiple symbols.Pattern of inter-relationships helps detect and correct errors.The length of shift register is called constraint (K=9) length.The longer the register, the better coding can correct bursty errorsHere, two symbols are generated for every bit input (Rate 1/2).

Full Rate Block InterleaveThe 384 modulation symbols in a frame are input into a 24 by 16 block interleave array and read down by columns, from left to rightAdjacent symbols are now separated in time This separation combats the effect of fast fadingA burst of errors could effect the area in red above and after the frame is written into the block de-interleave function at the mobile we see the errors are spread out instead of being in consecutive order.

Data Scrambling

Every 64th PN chip is modulo-2 added to a symbolRandomize transmitted dataEffects of all 1s or 0s' traffic (impulse-like) is reduced as the stream of ones or zeros will cause that the receiver may loss the synchronization with the transmitter as there is any changes in transmitted dataEliminates probability of Pilot Reuse ErrorMobile might demodulate a distant cell with same PN offset

Power Control Sub-channelA power control sub-channel is transmitted continuously every 1.25ms (or 800HZ)BTS instruct MS to change its power level by +1dB. A 0 power control bit requests the MS to increase its power. A 1 power control bit instruct the MS to decrease its powerEach power control bit has a bit time of two of data bit (for Rate set 1)A puncturing technique: The 1/(64*24) long code is used to randomize the position of the power control bit

Composite I and QEach channel card has a combiner and works in a serial array to combine the I and Q signals for all forward channels in a partition sector or cell.

The base band I and Q signals for all channel cards are sent to the CORE module to be multiplexed together based on the PN offset.

This ensures that a mobile station does not mistakenly decode the signal from a channel with the same Walsh code from the wrong base station.

Quadrature Phase Shift Key (QPSK) ModulationQPSK output = I cos ( 2 p fc t ) + Q sin (2 p fc t ) EveryChannelWalshcodeQ PN CodeI PN CodeBase band filterBase band filtercos ( 2 pfct ) sin (2 pfct ) SSSGain Control

Reverse Traffic Channels

Used when a call is in progress to send:Voice traffic from the subscriberResponse to commands/queries from the base station Requests to the base station

Supports variable data rate operation for:8 Kbps vocoderRate Set 1 - 9600, 4800, 2400 and 1200 bps13 Kbps vocoderRate Set 2 - 14400, 7200, 3600, 1800 bps

Reverse Traffic Channels

Rate 1/3 Convolutional Encoder

Block Interleaving The 576 modulation symbols in a frame are input into a 32 by 18 block interleave array read down by columns, from left to right

64-ary Orthogonal ModulationFor every six symbols in, 64 Walsh Chips are outputSix symbols are converted to a decimal number from 0-63The Walsh code that corresponds to the decimal number becomes the output

Direct Sequence SpreadingOutput of the randomizer is direct sequence spread by the long codeThe mobile station can use one of two unique long code masks:A public long code mask based on the ESNA private long code mask

Offset Quadrature Spreading & Baseband FilteringThe channel is spread by a pilot PN sequence with a zero offsetBaseband filtering ensures that the waveform is contained within the required frequency limitsBaseband signals converted to radio frequency (RF) in the 800 MHz or 1900 MHz range

Access ChannelsUsed by the mobile station to:Initiate communication with the base stationRespond to Paging Channel messages

Has a fixed data rate of 4800 bps

Each Access Channel is associated with only one Paging Channel

Up to 32 access channels (0-31) are supported per Paging Channel

Message attempts are randomized to reduce probability of collision

Two message types:A response message (in response to a base station message)A request message (sent autonomously by the mobile station)

Access Channel Generation

Summarization of Initialization of the Mobile StationSearch for the CDMA carrier, acquire the pilot channel and synchronize the short code.Receive the synchronous channel message containing the LC_STATE, SYS_TIME, P_RAT.Acquire timing and synchronize with the system.Monitor the paging channel and receive the system message.The mobile station can register and be taken as the calling party or called party.

Difference between IS95A and IS-95BWhat is IS95B

IS-95B is based on and compatible completely with IS-95A.

The main difference :

Increase the supplemental code channels to enhance the data rate. A single user can be assigned less than 8 code channels (1 FCH + 7 SCCH)the highest data rate being 76.8 (rate set 1) / 115.2kbps (rate set 2).

Soft handoff with relative thresholds

MS-aided hard handoff

Overview of CDMA 1XCompletely compatible IS-95A/BAdding multiple channels to improve the system performanceChannel bandwidth: 1.23MHzMaximum rate supported:307.2kbpsVoice code: 8K/13KQCELP 8K EVRCForward transmit diversity mode: OTD, STSModulation modeReverse HPSK: Forward QPSKPower control: forward/reverse power controlChannel code: Convolutional code and TURBO codeDemodulation mode: pilot-aided coherent demodulationCDMA 20001X

CDMA2000 1xIntroduction to CDMA2000 1x

Migration from IS95A to CDMA2000x

New features in CDMA2000x

Turbo CodeUse a Turbo code during the transmission of a large data packet.

Characteristics of the Turbo code:

The input information shall be encoded twice and the two output codes can exchange information with each other during decoding.The symbol is protected not only by the neighborhood check bits, but by the other check bits.

The performance of a Turbo code is superior to that of a convolutional code.

Variable Walsh CodesData rate -bps-The different Walsh codes corresponding to different data rates

Reverse HPSK Modulation

The CDMA 1X adopts forward QPSK modulation like the IS-95 system, but adopts HPSK modulation in the reverse.

HPSK ( Hybrid PSK ), namely, OCQPSK ( Orthogonal Complex QPSK ). The functions are as follows: Reduce the linear requirement for the power amplification of a mobile station.

Transmission DiversityThe forward transmission diversity types of CDMA2000 1XTD(Transmit Diversity)OTD(Orthogonal Transmit Diversity)The data stream is divided into two parts, which will be spread by the orthogonal code sequence.STS(Space Time Spreading)All the forward code channels are transmitted on the multi-antennas.Spread with the supplementarity Walsh code or with pseudo-randomization code.Non-TD

Transmission Diversity The Transmission Diversity Technology enhances the receive performance of a terminal.

advantages of the CDMA20001x Standards

Increased mobile standby battery life (via Quick Paging Channel)

Total backward compatibility to reuse switch and call processing features

No need to change any RF infrastructure

2-3 dB better coverage

High speed packet data capabilities

CDMA 2000 1XRtt New Channel Structure

CDMA2000 1x Rtt Channel

Forward Supplemental Channel (F-SCH)Assigned for high-speed packet data (>9.6 kbps) in the forward direction; (FCH is always assigned to each call)Up to 2 F-SCH can be assigned to a single mobileSCH cannot exist without having a fundamental channel establishedF-SCH supports Walsh code lengths of 4 - 1024 depending on data rate and chip rate

Reverse Supplemental Channel (R-SCH)Used for high-speed packet data (>9.6 kbps)Difference between F-SCH and R-SCH is in Walsh code based spreading

F-SCH supports Walsh code lengths of 4 to 128 (1xRTT) or 1024 (3xRTT) depending on data rate and chip rateR-SCH uses either a 2-digit or 4-digit Walsh code; rate matching done by repetition of encoded and interleaved symbolsWalsh code allocation sequence is pre-determined and common to all mobilesUsers are differentiated using long PN code with user mask

Reverse Pilot Channel (R-PICH)

Mobile transmits well-known pattern (pilot)

Allows base station to do timing corrections without having to guess where mobile is (in search window)

Mobile can transmit at lower power, reducing interference to others

Quick Paging Channel (F-QPCH)More efficient monitoring of paging channel by mobile, enhancement to slotted pagingMobile monitors QPCH to determine if there is a page forthcoming on paging channel in its slot (looks at 1-bit paging indicator)If no flag, then mobile goes back to sleep; if flag, then mobile monitors appropriate slot and decodes general page messageWithout QPCH, mobile must monitor regular paging channel slot and decode several fields to determine whether page is for it or not; this drains mobile batteries quicklyThe main purpose of QPCH is to save mobile battery life.

F-CPCCH

Common Power Control Channel tightly controls power of mobiles accessing the system using R-EACH or RCCCH

One CPCCH can transmit power control data for up to 24

reverse channels (each is either an R-EACH or an RCCCH) 12 channels of power control on the I channel, 12 on the Q channel

The CPCCH increases system capacity by better control of mobile power during access mode

F-BCH and F-CCCH

Broadcast Channel F-BCH40 ms frames with slots of 40, 80, or 160 msCarries only Overhead messages transmitted at 19.2, 9.6, or 4.8 kbps

Common Control Channel Uses 20, 10, or 5 ms framesTransmits signaling messages at 9.6, 19.2, or 38.4 kbpsHandles all other signaling directed to mobilesFree to operate at higher data rates to improve throughput

F-FACHWhat is F-CACH

F-CACH modes:

Power Controlled access modeF-CACH provides fast acknowledgments to mobiles during access for power control Reservation Access ModeTransmits an abbreviated address for each mobile that is allowed to transmit on the R-CCC . This reduces collisions during the access process

CDMA key technologies

Power control

Handoff

Why Power Control?All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminators.CDMA operates by using CODES to discriminate between users.CDMA interference comes mainly from nearby usersEach user is a small voice in a roaring crowd -- but with a uniquely recoverable code.Transmit power on all users must be tightly controlled so their signals reach the base station at the same signal level and at the absolute minimum power level necessary to ensure acceptable service quality

Reverse Open LoopThe mobile station makes a coarse initial estimation of the required transmit power, based upon the total received power.

Problems with Reverse Open Loop Power Control: Assumes same exact path loss in both directions; therefore, cannot account for asymmetrical path lossEstimates are based on total power received; therefore the power received from other cell sites by mobile station introduces inaccuracies

Reverse Closed Loop Power ControlCompensates for asymmetries between the forward and reverse pathsConsists of power up (0) & power down (1) commands sent to the mobile stations, based upon their signal strength measured at the Base Station and compared to a specified thresholdEach command requests a 1dB increase or decrease of the mobile station transmit powerTransmitted 800 times per second, always at full powerAllows to compensate for the effects of fast fading

Reverse Outer Loop Power ControlMost gradual form of reverse link power controlSet point is varied according to the FER on the Reverse Traffic Channel (determined at the Base Station Controller)Sampled at a rate of 50 frames per second (20 ms / frame)Set point adjusted every 1-2 seconds

Forward Traffic Channel Power ControlThe base station slowly decreases power to each mobile station.

As the FER (determined at the mobile station) increases, the mobile station requests a Forward Traffic Channel power increase.

Summary of All Power Control MechanismsAll types of power control work together to minimizes power consumption at the mobile stations, and increases the overall capacity of the system transmit power.

HandoffsHandoff is the process by which a mobile station maintains communications with the Mobile Telephone Switching center(MSC), when traveling from the coverage area of one base station to that of another.

Handoffs keep the call established during the following conditions:Subscriber crosses the boundaries of a cellSubscriber experiences noise or other interference above a specified thresholdA base station component experiences an out-of-service condition during a call

CDMA HandoffsCDMA HandoffsMake-before-break Directed by the mobile not the base stationUndetectable by userImproves call qualityHandoffs consist of the following phases:Initiation (trigger), Target Selection, and Completion (execution)

CDMA Handoffs (cont.)

Soft HandoffSoft Handoff: the mobile station starts communications with a target base station without interrupting communications with the current serving base station. Can involve up to three cells simultaneously and use all signalsMobile station combines the frames from each cell

Softer HandoffHandoff is between sectors of the same cellCommunications are maintained across both sectors until the mobile station transition has completedMay happen frequentlyMSC is aware but does not participateAll activities are managed by the cell siteSignals received at both sectors can be combined for improved quality

Inter-System Soft Handoffs Mobile Station starts communications with a new cell controlled by a different BSC while still communicating with the cell controlled by the source BSCSoft Handoffs over Hard HandoffsFewer border cell

Hard HandoffBetween cells operating on different frequenciesBetween cells that could be on the same frequency, but which are subordinated to different MSC

Pilot SetsPilot sets:Active Set: Pilots associated with the forward traffic channels assigned to the mobile station (max 6 pilots)Candidate Set: Pilots not currently in the Active Set, but received by the mobile with sufficient strength to indicate that the corresponding Traffic Channels can be successfully demodulated (max 5 pilots)Neighbor Set: Pilots not currently on the Active or Candidate Sets, that are likely handoff candidates (at least 20 pilots)Remaining Set: All other possible pilots in the current system on the current CDMA frequency assignmentAll pilots in a set have the same frequency assignmentThese sets can be updated during handoff by the base station

Pilot Set Initialization (While in the Idle or in an Active Call)

Pilot Set Maintenance (While in an Active Call)

Pilot Strength Measurement Message (PSMM)The Pilot Strength Measurement Message is used by the mobile station to direct the base station in the handoff process.Mobile station reports the strength of the pilots associated with forward traffic channels currently being demodulated (and whether it would like to continue to receive traffic from them), as well as pilots from the neighbor and remaining list which are being received with sufficient strength so that traffic could be demodulated from them successfully.

Pilot Search WindowsA search window is a range of PN offsets (in chips) where the mobile station searches for usable multipath components of the pilots in a setUsable means that multipath components can be used for demodulation of an associated traffic channel

Soft Handoff SignalingT_ADD: pilot detection thresholdT_DROP: pilot drop threshold T_TDROP: drop timer value Prevents unnecessary transmissions of PSMM when a mobile station experiences a fade

Thanks!

IMSI is the only number to identify a mobile user in a CDMA digital public land cellular mobile communication network. This code is valid to all location including a roaming area.IMSI adopts E.212 coded system.IMSI is stored in the mobile station/UIM card, HLR and VLR and transmitted on a wireless interface and MAP interface. Unicom uses MIN-based IMSI. IMSI is a 15-digit decimal number and its number structure is shown in the figure.MCC: Mobile Country Code, 460 for China.MNC: Mobile Network Code03 used in Unicom CDMA.MSIN: Mobile Subscriber Identification Number, a 10-digit decimal number. Unicom requires that MIN is the latter 10 digits of an IMSI, namely, MSIN.For the users of in the original Great Wall network in Unicom, the MSIN number structure is shown below: 3 + H1H2H3 + ABCDEF H1H2H3 equals that in a MDN.ABCDEF is obtained after the scrambling of ABCD in a MDN.For new Unicom users, MSIN is the IRM number resource obtained by China Unicom. Unicom first uses the number segment between 09 1000 0000 and 09 4999 9999 and the number structure is as follows: 09 + M0M1M2M3 +ABCDM0M1M2M3: the same as the H0H1H2H3 in a MDN. (Note: in the number segment first used by Unicom, M0M1M2M3 may be the same as H0H1H2H3. Because the IRM number obtained by China Unicom is a discontinuous number segment. In the number segment used at a late time, M0M1M2M3 and H0H1H2H3 are different.ABCD: user number, to be obtained based on the scrambling of ABCD in a MDN in a certain mode, the scrambling mode to be defined by Unicom headquarters.

MDN is the number the caller needs to dial when a mobile user in home network is the called. MDN adopts E.164 coded system.MDN is stored in HLR and VLR, and transmitted on an MAP interface. The structure of a MDN is shown in the figure.CC: country code, 86 used in China.MAC: Mobile Access Code, network number plan adopted in home network, 133 used in China.H0H1H2H3: HLR identity number, allocated by Unicom headquarters on a uniform basis.ABCD: mobile user number, allocated by various HLRs.H0H1H2H3 China Unicom allocation plan:This allocation plan takes into consideration IRM (international roaming MIN) number resource and user development prediction controlled by China Unicom. In actual applications, the starting point should be H0 equal to 0~9 and MDN can be gradually used. Currently, the number segment with H0 equal to 0 is used by users in the original Great Wall network and includes TLDN number and user number. For allocation arrangement, refer to the requirements of the Great Wall network. The numbers with H0 equal to 1~9 are used new users. The allocation plan of H0H1H2H3 is decided by Unicom headquarters on a uniform basis.

In a CDMA network, a mobile station judges whether roaming takes place based on a pair of identity numbers (SID and NID). System Identity Number (SID) includes 15 bits. Unicom first uses 512 numbers (3600~37FF) with bit 14~bit 9 being 110010. Each local mobile network is allocated with one SID and the specific number allocated to each local network is specified by Unicom headquarters. Network Identity Number is made up of 16 bits, with 0 and 65535 reserved. 0 is used to represent those base stations in a certain SID area not belonging to a specific NID area. 65535 is used to indicate that a mobile user can roam in the whole SID area.For a CDMA network side, there is no concept of NID, but an exchange number (one byte), which is used to identify the network equipment where a user is located. ATM (Asynchronous Transfer Mode) is a high speed packet switching technology. It supports any kind of service.

VPI:Virtual Path IdentifierVCI:Virtual Channel IdentifierATM is a circuit switched procedureThe connection through ATM network is called as virtual, since it does not exist physically, but it is present only in the form of routing tables in the switching center. Traditional Switch Module:Circuit switching, data is sent on the same route. GFC ( Generic Flow Control): Supports the configuration of the subscriber equipment. It is intended for the control of a possible bus system at the user interface.VPI ( Virtual Path Identifier): VPI contains the second part of the addressing instructions and is of higher priority than the VCI. This allows the rapid direction of the cells through the network. ATM cross-connects the cell stream in various directions based on VPI. The VPI and VCI are assigned by the switching centers when the call is being established.VCI ( Virtual Channel Identifier): This field contains part of the addressing instructions. All cells belonging to the same virtual channel have the same VCI. VCI indicates a path section between switching centers or between switching center and subscriber. PTI ( Payload Type Identifier): A distinction is made between network and user information.CLP ( Cell Loss Priority):The contents of this field determines whether a cell can be preferentially deleted or not during congestion. CLP=0 Lower priorityCLP=1 Higher priorityHEC ( Header Error Control): The HEC is used to synchronize the receiver to the start of the cell. CRC code is also sent over it (x8+x2+x+1)

There are cells for transmitting the signaling information and OAM cells. VCVirtual Connection SSCS:Service Special Convergence Sublayer CPCS:Common Part Convergence Sublayer CS:Convergence Sublayer SAR:Segmentation And Reassembly AAL:ATM Adaptation Layer PHY:Phsical Layer TC:Transmission Convergence Sublayer PMD:Physical Medium Dependent Sublayer HEC: Header Error Control This page reference page :AAL5 Process.ReferenceRFC1483SNAP: Sub-network Access Protocol LLC: Low Layer CompatabilityFrequency Division Multiple Access: frequency division, sometimes called channelization, means dividing the whole available spectrum into many single radio channels (transmit/receive carrier pair). Each channel can transmit one-way voice or control information. Under the control of the system, any user can be accessed to any of these channels. Analog cellular system is a typical example of FDMA structure. Similarly, FDMA can also be used in a digital cellular system,except that pure frequency division is not adopted. For example, FDMA is adopted in GSM and CDMA.Time Division Multiple Access means that the wireless carrier of one bandwidth is divided into multiple time division channels in terms of time (or called timeslot). Each user occupies a timeslot and receives/transmits signals within this specified timeslot. Therefore, it is called time division multiple access. This multiple access mode is adopted in both a digital cellular system and a GSM. TDMA is a complex architecture and the simplest case is that a single channel carrier is divided into many different timeslots, each of which transmits one-way burst-oriented information. The key part in TDMA is the user part, in which each user is allocated with one timeslot (allocated when a call begins). The user communicates with a base station in a synchronous mode and counts the timeslot. When his own timeslot comes, the mobile station starts a receiving and demodulation circuit to decode the burst-oriented information sent from the base station. Likewise, when a user wants to send any information, he should first cache the information and waits for his timeslot to come. After a timeslot begins, the information is transmitted at a double rate and next burst-oriented transmission begins to be accumulated. CDMA is a multiple access mode implemented by different code sequences formed by means of spreading technologies. Unlike FDMA and TDMA, both of which separate the user information in terms of time and frequency, CDMA can transmit the information of multiple users on a channel at the same time. That is to say,mutual interference between users is permitted. The key is that any information before transmission should be coded specially and the information after the coding, when mixed, will not lose any original information. The number of orthogonal code sequences is the same as that of users communicating on a carrier at the same time. Each transmitter has its only code (pseudo-random code) and also knows the code to receive . Using the code as a signal filter, a receiver can restore to the original information code (this process is called despreading) from the background of all other signals. CDMA includes two basic technologies, one being the multiple access technology and the other being the spreading technology. The multiple access technology can be implemented by means of spreading to enable different user information to be separated and transmitted on the same frequency and at the same time. However, the spreading technology can reduce noise interference greatly.

Because CDMA system can use same spectrum in adjacent cells, so the network planning of CDMA system is simple. And you can save the frequencies source.In China Unicom phase 1 project, 1500 lines, only use one frequency point: 283. And in Shenzhen, the most advanced and rich city of China, ZTE provides the CDMA equipment for China telecom, now has 150000, only uses two frequencies points: 975 and 950. Why? Because CDMA is a self-interfere system, the frequency reuse is 1, if there is not many users in one area, you can only use one carrier.

CDMA system supply better voice quality.Lets look the figure , this shows the voice quality of 64k(kilo) PCM,this shows the voice quality of GSM system , this shows the voice quality of 8k(kilo) evrc CDMA system.

Increase in the rate of time domain signals means the spread of bandwidth of frequency domain signals. This demands spreading technologies. One important application of spreading is to solve the problem of reliable communication when there is strong interference. Meanwhile, the spreading technologies adopted in CDMA has such a feature: despreading and spreading calculations are the same. Let us suppose that the broadband signals we receive are accompanied by strong narrow-band interference signals, as shown in Figure 3. Thus, the process of despreading converts the input signals into a useful narrow-band signal and multiple broadband signals (the narrow-band interference signals after the despreading become broadband interference signals with greatly reduced strength). After the narrow-band filter calculation, only the energy of a small number of interference signals passes a filter and becomes remaining interference. Thus, interference is greatly reduced. In CDMA, the above goal of spreading can be achieved by means of QPSK modulation. CDMA system is a broadband system, that is to say, the bandwidth of one carrier in IS95 is made to reach 1.25MHz. Therefore, we say this system itself integrates the function of frequency diversity. We say this based on the following reasons: Suppose how the frequencies of 900M and 900.001M are transmitted in air. If fading occurs to the frequency of 900M,we think that the frequency of 900.001M will also fade. In this case, if the two frequencies are used for signal diversity, we do not think we will succeed. That is to say, when frequency 1 fades, frequency 2 will fade at the same time and cannot overcome the fading. Then suppose how the frequencies of 900M and 910M are transmitted in air. If fading occurs to the frequency of 900M, the frequency of 910M may not fade as a result of different transmission performance. In this case, if the two frequencies are used for signal diversity, we can achieve the goal. CDMA uses Rake receiving technology, like the photos, the Base Station transmits the signal to the MS, through the 3 paths, d1,d2,d3, so in the MS side, the receiving signal is like the photo of receiving, the signal gotten from the 3 paths is not at the same time, it causes the distortion. Through the Rake combination, by the help of pilot signal, MS uses rake combination, and by changing the 3 signals phase, the 3 signals overlap together, and get a much strong and the same phase of transmission signal, and the S/N has been improved greatly. By the method of Rake receiver, we get a much better S/N, and overcome the different time delay of the signals gotten from the different paths.

There are 8 band classes stipulated in the IS-2000 for the working frequency band of the CDMA2000:1. Band Class0: Corresponding to the North America cellular frequency band, also in use in China, Hong Kong, Australia, North Korea and Taiwan.2. Band Class1: Corresponding to the PCS frequency band in North America.3. Band Class2: Corresponding to the TACS frequency band.4. Band Class3: Corresponding to the JTACS frequency band.5. Band Class4: Corresponding to the PCS frequency band in South Korea.6. Band Class5: Corresponding to the NMT-450 frequency band. (Nordic Mobile Telephone)7. Band Class6: Corresponding to the IMT-2000 frequency band.8. Band Class7: Corresponding to the 700MHz cellular frequency band in North America.Convolutional code is an error correcting code. Convolution aims to associate a previous signal with a subsequent one which means that this signal is capable of detecting and/or correcting an error. Error correcting or error detecting certainly will increase some redundancy signals, therefore the output bit rate increases to 3 times that at the input terminal of a convolutional encoder. It can be seen from the figure that the data are read row by row into an interleaver at the transmit end,read column by column out (this process is called interleaving) and propagated after other modulation process. Then, the data enter the interleaver at the receive end row by row and are read out column by column (this process is called de-interleaving).Currently, we assume that in the course of propagation, when row 2 data are transmitted, consecutive error codes occur to the 2nd, 3rd and 4th bits as a result of fading or other reasons, as shown by the left side of the figure. If the original data had been transmitted after the interleaving, the second bit of row 2 ,the second bit of row 3 and the second bit of row 4 would have been error codes after being read out column by column at the receive end. Because common error correcting codes can very easily process discrete error codes, the receive end can very easily recover the signals after the anti-interleave into the original signals by means of error correcting,but always cannot recover those signals not interleaved as a result of consecutive error codes. Therefore, the interleave can overcome fast fading caused during the signals transmission in air. The interleave code seldom functions in correcting error codes caused by slow fading, because slow fading may result in long consecutive error codes,even the whole frame may be error.Therefore, there will occur consecutive error codes after de-interleaving . The above figure is the simplest interleave and the interleave in an actual application is far more complex.The above figure shows the case in a reverse direction, in which the 6 input symbols become 64 chips. In a forward case, similar to the spreading described previously, each symbol become 64 chips after spreading with 64-order Walsh Code .As opposed to the data modulated by I pilot PN sequence, the data modulated by Q pilot PN sequence has the delay of half a PN chip (406.901ns). Thus, the maximum phase change of four-phase modulation is 90 degrees instead of 180-degree mutation.

In an actual application, the system implements the modulation in this way: as shown above, I and Q channel sequences in the figure represent two channels of cyclic PN short code sequences. The cyclic period of each channel of PN short codes is 215. For different sectors, there are different starting locations of I and Q sequence cycles (that is to say, different sectors have different time offsets). In this way, different PN short code sequences can be obtained and a mobile station can recognize the information from different sectors.In CDMA 1X system, different users are allocated with different information rates by means of variable-length WALSH codes. However high a rate each user finally obtains is, the chip rate received by each user is 1.2288M. Therefore, for a user obtaining the final information rate of 153.6Kbps, the length of a received WALSH code is 4-bit instead of 64-bit. Accordingly, the spreading gain is only 10log10 (1.2288M/153.6K)=9. That is to say, the spreading gain is reduced. In the example, Mobile 1 shows currently supported scenario (an FCH is always assigned for each call: data or voice). Note however, that (for now) simultaneous voice and data calls are not supported.SCHs cannot be assigned without some other FCH being assigned as well.Here is the first mention of variable length Walsh codes. Its probably enough to know that Walsh code length for data calls is variable at this point. Implementation and rationale for Walsh codes of varying length is discussed later.Note that Walsh codes are now used explicitly in the reverse direction. This is because there are now more than one reverse channel, and they need to be distinguishable from one another.QPCH is an enhancement to slotted paging.Instructor, some possible questions to be ready for:How much is QPCH apt to extend a mobiles battery life? As long as theres no configuration change information for the mobile to capture, the mobiles only going to be monitoring 2 bits vs. an entire slot. This equates to up to 40% decrease in the amount of battery power used to monitor an IS-95 paging channel with slotted paging implemented. Once the mobile is involved in a call, however, the story changes considerably because of all the extra channels itll be forced to use (in both directions).Is QPCH optional? Yes; its up to the network operator to implement use of QPCH or not. Slotted paging can take as much as 5 sec. However, its estimated that QPCH will add at most 100ms to the time it takes to page a mobile using regular slotted paging.Is QPCH used to alert a mobile in the MAC dormant state that theres more data for it? How long might it typically take to re-establish the MAC active state and resume data transfer? QPCH (if enabled, otherwise the paging channel) is indeed used to re-establish the MAC active state and data transfer (in the forward direction; in the reverse, the mobile makes a standard call origination request). The scheme is exactly as it would be if the mobile were responding to a page, or originating a new call. However, network operators may want to opt for shorter mobile sleep times (at the expense of mobile battery life) to reduce the amount of time data transfer re-establishment takes.

New_ CDMA Material (LT)v

Documents

Transcript of New_ CDMA Material (LT)v