What we will talk about and who is doing the talking

Vice President of Technology – CoachComm LLC. Auburn, AL

30 years of RF and wireless technology experience

Rental Mgr, Freelance RF, Product Mgr wireless/wired intercom, Engineering Mgr, Speaker, Author

Systems Wireless, DTC, Talamas, Telex/RTS, CoachComm

CoachComm designs and manufacturers Tempest wireless intercom CoachComm has two main markets

Sideline football coach communications

For Universities, Colleges, High Schools, and other programs

Wireless communications for Broadcast, Live, and Industrial Applications

Distributed by Clear-Com worldwide

The current state of the UHF spectrum Changes in regulations

Less spectrum to go around

Additional users vying for space

Potential alternatives to UHF spectrum – unlicensed spectrum

Technology challenges and considerations related to unlicensed wireless use

Digital RF techniques to overcome these challenges

Practical tips and recommendations

UHF Spectrum Use

Things are not getting easier in our traditional spectrum

Initial auction eliminated 108MHz of UHF spectrum 698 – 806 MHZ gone - AT&T, Verizon, etc…

Incentive Auction looming Nobody really knows what’s going to happen

Likely at least another 100MHz or more gone

White Space devices The great unknown!

UHF and VHF, mobile and fixed

Much less spectrum… many more users Production demands for wireless aren’t going down

Other non-production devices added in

All wireless audio devices are not created equal

On-air devices Wireless microphones primarily

Extremely low latency

Audio frequency response 40Hz – 12kHz or better

Audio dynamic range 90dB or better

Extremely high fade margin

Extremely low tolerance for hits

FM analog UHF only real option at this time

Talent devices Wireless IFB, In-ear monitors primarily

Very low latency

Audio frequency response 80 – 8kHz or better

Audio dynamic range 90dB or better

High fade margin

Low tolerance for hits

Very few options other than FM analog UHF at this time

Communication devices Wireless intercom primarily

Some latency acceptable

Audio frequency response 300 – 4kHz or better

Audio dynamic range 80dB or better

Lower fade margin

Higher tolerance for hits

cannot compromise communications

Non-UHF options are available

Some are even better than current UHF implementations

Good candidate to migrate out of UHF spectrum

UHF wireless intercom is spectrally inefficient 8 wireless beltpacks use between 12 and 16 frequencies

Requires free spectrum in different locations

Migrating UHF wireless frees up a LOT of spectrum Moving 8 UHF wireless intercom beltpacks frees up 12 to 16 UHF

frequencies for wireless mics/IFBs

Huge impact on ability to provide wireless mics/IFBs

Moving wireless intercom out of UHF is smart

If not the traditional UHF spectrum, where do we operate

Some available options 902 – 928MHz (900MHz)

1880 – 1930MHz (1.9GHz)

2400 – 2495MHz (2.4GHz)

5725 – 5875MHz (5.8GHz)

Which is best All have advantages and disadvantages

World-wide operation 900MHz

North America, Australia, some of South America

1.9GHz

Most areas of the world – spectrum varies from place to place

1880MHz–1900MHz in Europe – 1900MHz-1920MHz in China

1910MHz-1930MHz in Latin America – 1920MHz–1930 MHz in US/Canada

2.4GHz

World-wide approval – spectrum is generally the same

Some limitations

5.8GHz

Approval varies widely and is changing quickly

Amount of spectrum available 900MHz

26MHz

1.9GHz

10 to 20MHz depending on location

US only 10MHz

2.4GHz

80 to 95MHz with very few exceptions

5.8GHz

150MHz or more but varies

Propagation characteristics Generally, higher frequency = poorer propagation

900MHz acts more like traditional UHF

5.8GHz suffers from body shielding and severe multipath

1.9GHz and 2.4GHz strike a balance

Regulatory constraints transmitter power, modulation techniques, interoperability

requirements…

900MHz, 2.4GHz, 5.8GHz sharing mandated

1.9GHz somewhat similar, audio only

Competition for spectrum use Virtually all of these bands are being heavily utilized

Licensing requirements All of these bands do not require a license for use

Conclusion 2.4GHz offers the best balance of all factors for world-wide use

900MHz offers a good alternative for North America

Technology is readily available for both

Several manufacturers have adopted one or both

The challenges and solutions to working in an unlicensed spectrum

Lots of users vying for spectrum Wi-Fi 802.11 b/g

Bluetooth

Wireless cameras

Wireless DMX

Microwave ovens

Many Others…

Limited propagation characteristics More problematic with 2.4GHz than 900MHz

Multipath fading

Object penetration (900MHz is much better in this regard)

Regulations require devices to “share” Spread spectrum technology

Major spread spectrum technologies Frequency Hopping (FHSS)

Bluetooth

Some wireless cameras

Some wireless intercoms

Direct Sequence (DSSS) & Orthogonal Frequency-Division Multiplexing (OFDM)

Wi-Fi, 802.11 b/g/n etc.

Devices that “ride along” on Wi-Fi

What is FHSS Seeks to use as much spectrum as possible over time

Uses a very narrow portion of the spectrum at any instance

Narrow band transmission

Changes frequencies “hops” periodically

Pseudorandom hopping pattern

Sequence must be known by base and remote

Remote must be synchronized “paired” with base prior to use

FHSS implementations vary greatly Some are more successful than others

Over time 80MHz of spectrum is used◦ 2400 – 2480MHz

Only 1.3MHz is used at one time◦ Narrowband operation

◦ Wi-Fi is 20 or 22 or 40 MHz

Changes frequencies or hops 200 times/sec◦ 5ms dwell time

Gaussian Frequency Shift Keying (GFSK) Relatively simple modulation scheme

Uses optimal modulation index

Enhance receiver sensitivity in presence of noise

Resists narrowband fading (Rayleigh fading)

Narrowband transmission Concentrates RF energy in one specific area of spectrum

Maintain robust wireless link in the face of interference and noise

Changing frequencies “hopping” Less susceptible to

single point external interference sources

Intermodulation products

Multipath fading (Rayleigh fading)

FHSS is inherently 1 to 1 technology

Time Domain Multiple Access (TDMA) Enables multiple users

All users operate on the same frequency

Users share the frequency one at a time

Very different from FHSS

Does not seek to use as much spectrum as possible over time

Spreads RF power over a wider, fixed area◦ Wideband transmission

◦ Spreading versus hopping

DSSS spreads the data using a pseudorandom “noise” signal Much higher frequency than data signal

OFDM spreads the data using multiple orthogonal carriers Effectively produces a signal spectrally similar to DSSS but with many

advantages

Total RF power is similar to FHSS

RF power at any given frequency is much less

Resembles white noise to a well designed FHSS device

De-spreading requires TX-RX synchronization Usually a timing search process

The FHSS system above may not work very well on its own

Technology enhancements are necessary for robust, reliable operation

Redundant Data Transmission (2xTX) – 2.4GHz only All data is sent twice

Once from each antenna

On consecutive hops (different frequencies, different moments in time)

Halves spectral efficiency

Redundant Data Transmission (2xTX) 2.4GHz only Dramatically reduces Effective Packet Error Rate (EERP)

One RF packet loss is common

Pseudorandom frequency hopping pattern separates consecutive transmissions

This frequency relationship prevents multiple consecutive packet loss

Two consecutive RF packets must be lost before an audio packet is lost

Extremely important for 2.4GHz success

Dual antenna diversity – 2.4GHz only Adds spatial and polarization diversity to frequency and time diversity

Makes for a very robust RF link

Lost Packet Concealment (LPC) Packet loss is inevitable

Allows some audio packets to be lost or damaged without noticeable impact on user audio

Algebraic – Code Excited Linear Prediction (A-CELP)

At least four consecutive RF packet loss before an noticeable impact on audio is heard

The practical application of technology for success in the 2.4GHz and 900MHz bands

Can a well designed FHSS wireless intercom peacefully coexist with an extensive 802.11 b/g/n Wi-Fi network?

Yes…

Wi-Fi overview 14 channels world-wide

13 in most locations

11 in the US

Each channel is 20 or 22 or 40 MHz wide (our FHSS 1.3MHz)

Only 3 non-overlapping channels 1, 6, 11 (14 in Japan)

Wi-Fi uses 3 non-overlapping channels: 1, 6 and 11

Wi-Fi signal characteristics vary greatly depending on network traffic Worst case scenario is maximum network data throughput

Signal appears to be higher power and more dispersed

Normal web surfing does not typically produce this condition

Even with lots of users

Large file transfers create this condition

Becoming more common as video streaming increases

Our FHSS/TDMA RF design with enhancements works and plays well with Wi-Fi RF power is concentrated into a small area of spectrum

Wi-Fi RF power is spread over a much larger area of spectrum

Wi-Fi appears as background noise to our FHSS design

Greater perceived RF power at any given frequency allows our FHSS design to penetrate through the Wi-Fi signal

Wi-Fi is not significantly affected by our FHSS design

Each hop is a small portion of the Wi-Fi signal

Spreading of the data means that all of the data gets through

Best practices for coexistence Get as much physical distance as possible

50 feet minimum

Consequences of coexistence Our FHSS system degradation

Shortened range

Digitized sounding audio

Logging in and out

802.11 b/g/n Wi-Fi

Reduction of network throughput of 10% (90% capacity)

Only noticeable at maximum network loading

Constrain our FHSS to a limited portion of the band

Allows system to avoid one or more Wi-Fi chans

Limits hoping pattern

Usually best to use the whole band

7 bands available in our design

MHz

Band Chan Start End Wide Avoid 802.11b/g

1 43 2400 2480 80 None

2 27 2400 2450 50 11

3 27 2423 2473 50 1

4 27 2431 2480 49 1,2

5 15 2400 2428 28 7,8,9,10,11

6 15 2423 2450 27 1,11

7 15 2453 2480 27 1,2,3,4,5,6,7

2.4GHz Tempest One base supports up to 5 normal mode users

One base supports an unlimited number of shared users

Limited to five talkers per base at any given time

Up to 11 collocated bases

Up to 55 normal mode wireless users

Unlimited number of shared mode wireless users

900MHz Tempest One base supports up to 5 normal mode users

One base supports an unlimited number of shared users

Limited to five talkers per base at any given time

Up to 5 collocated bases

Up to 25 normal mode wireless users

Unlimited number of shared mode wireless users

Mixed 900MHz/2.4GHz system Up to 80 total wireless full duplex users

The presentation in a nutshell

UHF spectrum is becoming much more crowded and will continue to do so

Production requirements continually call for more wireless devices

Migrating wireless microphone and/or wireless IFB equipment out of the traditional UHF band is not practical at this time

Wireless communication equipment can be effectively migrated outside the UHF band

The 2.4GHz & 900MHz bands are excellent candidates for wireless communications

Spread spectrum technology allows multiple users to better share a given portion of the spectrum

Choosing the right implementation of spread spectrum technology is important

FHSS technology wireless intercom systems help to enable collocation with 802.11b/g/n Wi-Fi and other devices

Other technologies and techniques must be utilized in conjunction with the base FHSS/TDMA RF scheme

Any Questions?