Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 1
Providing efficient and reliable multimedia telephony over HSPA
Stefan Wänstedt, Mårten Ericsson
Ericsson Research
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-092
Luleå
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 2
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-093
Outline
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-094
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
Outline
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 3
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-095
Why All-IP and MM Telephony?
§ All-IP means fixed-mobile convergence; one network for all traffic.
All-IP and MMTel
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-096
IMS = IP Multimedia Subsystem
P-CSCF
I-CSCFMRF
MGW
MGCF
IMSIMS
S-CSCF
SIP Application
ServersSIP Application
Servers
HSS
RNCMSC(Server)
SGSNGGSN
CNCNMGW
BSC
UMTS/GPRSUMTS/GPRS
§ A common architecture for service control of IP based services
§ Main track for delivery of new IP based services
§ (VoIP essential for convergence)
All-IP and MMTel
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 4
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-097
MM Telephony in WCDMA evolution
§ HSDPA – improved downlinkpacket-data support
– Reduced delays
– 14 Mbit/s peak data rate
– Flexible bit rate
– Increased capacity
§ Enhanced Uplink – improved uplink packet-data support
– Reduced roundtrip delays 30-50 ms end-to-end RTT possible
– High bit rate availability –5.76 Mbit/s peak data rate
– Flexible bit rate
– Increased capacity
Enhanced
Uplink
Rel 4 Rel 6R99
Enhanced Downlink
(HSDPA)
Rel 5
WCDMA WCDMA EvolvedEvolvedWCDMAWCDMA
Rel 7
MM Tel.
All-IP and MMTel
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-098
Why IMS VoIP?
§Fixed and mobile service convergence
§Possible to run all IMS services on the same transport– Add services during “call”
– Presence
§VoIP is integral service
All-IP and MMTel
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 5
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-099
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
Outline
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0910
Multimedia telephony
§ Telephony service with possibility of
– Flexible selection of media
– Add/drop of participants
§ Currently being standardized in 3GPP
§ Forms the foundation to create new rich services
– New applications created based on the MMTel
Mobile IP services
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 6
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0911
Presence/Active phone book
§ Active phone book shows contact list status
– Who is available
– For which service/media
§ Active phone book updated with the presence signaling
Mobile IP services
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0912
Changed way of communication
§ Start with contact list
§ See who is available
§ Select which service/media to use
§ Add another media
§ Add another session
Mobile IP services
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 7
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0913
RAN PS Domain IMS
Session control signaling SIP/SDP/UDP/IP
Media flow AMR/RTP/UDP/IP
Media control flow RTCP/UDP/IP
PS Domain RAN
Mobile IP services
VOIP data flow components
Presence flow not incuded in this figure
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0914
IP protocols are generous in size
§ More than half of a VoIP packet is IP header overhead
§ Call control using SIP/SDP is a chatty ASCII protocol
IP/UDP/RTP AMR
60 or 40 octets 32 octetsInvite till Ringing
Originating Terminating
NetworkUE
INVITE
183 PROGRESS
PRACK
200 OK (PRACK)
UPDATE
180 RINGING
PRACK
200 OK (PRACK)
200 OK (INVITE)
ACK
UE
200 OK (UPDATE)
Network …User A
initiates
se ssion
INVITE
Alerting
Accept
Conversation on
Alerting
Indication
Resource Allocation
Signalling Bearer
Resource Allocation
Signalling Bearer
Resource Allocation
Media Bearer
Resource AllocationMedia Bearer
Invite till RingingInvite till Ringing
Originating Terminating
NetworkUE
INVITE
183 PROGRESS
PRACK
200 OK (PRACK)
UPDATE
180 RINGING
PRACK
200 OK (PRACK)
200 OK (INVITE)
ACK
UE
200 OK (UPDATE)
Network …User A
initiates
se ssion
INVITE
Alerting
Accept
Conversation on
Alerting
Indication
Originating Terminating
NetworkUE
INVITE
183 PROGRESS
PRACK
200 OK (PRACK)
UPDATE
180 RINGING
PRACK
200 OK (PRACK)
200 OK (INVITE)
ACK
UE
200 OK (UPDATE)
Network …User A
initiates
se ssion
INVITE
Alerting
Accept
Conversation on
Alerting
Indication
NetworkUE
INVITE
183 PROGRESS
PRACK
200 OK (PRACK)
UPDATE
180 RINGING
PRACK
200 OK (PRACK)
200 OK (INVITE)
ACK
UE
200 OK (UPDATE)
Network …User A
initiates
se ssion
INVITE
Alerting
Accept
Conversation on
Alerting
Indication
Resource Allocation
Signalling Bearer
Resource Allocation
Signalling Bearer
Resource Allocation
Media Bearer
Resource AllocationMedia Bearer
INVITE sip:al@jaguar SIP/2.0From: SIP:bo@e005004b57366:5061To: sip:al@jaguarCall-ID: e53cdd755e5decf@e005004b57366CSeq: 1 INVITESubject: helloVia: SIP/2.0/UDP e005004b57366:5061Require: 100relContent-Type: application/sdpContent-Length: 208
Compression is needed
Mobile IP services
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 8
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0915
Robust Header Compression (ROHC)
40 or 60 14-32
3
Mobile IP services
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0916
VoIP bit rate example
12.2
Bit rate (DL) [kbps]
42
24
16 14
5
Time
VoIP Initial state with no header compression
Header compression active
DTX period
CS voice bit rate
Mobile IP services
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 9
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0917
The VoIP service - characteristics
§ AMR-NB and AMR-WB speech codecs
§ Low media bit rates– 4.75 to 12.2 kbps for AMR-NB– 6.60 to 15.85 (23.85) kbps for AMR-WB
§ Small payload sizes (BW efficient RTP payload format)– 14 to 32 bytes for AMR-NB– 18 to 41 (61) bytes for AMR-WB
§ Discontinuous transmission (DTX)– SID frames of 7 bytes sent in average every 160 ms during
silent periods
§ Speech frame length of 20 ms
§ Transport over RTP/UDP/IP protocols– Overhead of 40 or 60 bytes (IPv4 and IPv6, respectively)
Mobile IP services
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0918
The VoIP service - quality
§ Quality constraints set by CS services; PS flexible
§ Handles some packets losses
– For AMR 12.2, 2% packet loss is ”allowed”
§ End-to-end delay cannot be too large
– CS ~220ms
Mobile IP services
High Quality
CS equivalent Quality
Economy Quality
WB
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 10
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0919
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
Outline
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0920
Bearer alternatives
§ DCH
– “Circuit switched”
– Low delay
– Low bit rate flexibility
§ HSPA
– HSDPA and EUL
– Packet switched
– Varying delay
– High bit rate flexibility
§ MMTel requirement
– Varying bit rate
– Easy to add or delete services on the fly
HSPA Basics
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 11
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0921
§ Fast Link Adaptation
– Data rate adapted to radio conditions
– 2 ms time basis
§ Fast Retransmissions
– Roundtrip time ~12 ms possible
– Soft combination of multiple attempts
§ Shared Channel Transmission
– Dynamically shared code resource
2 ms
§ Short TTI (2 ms)
– Reduced delays
HSDPA - Basic Principles
TTI = 2 ms
Shared Multi-code
transmission (15 codes)
Link
Adaptation
Features
Hybrid ARQ with
Soft Combining in RBS
HSPA Basics
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0922
Enhanced Uplink - important principles
§ Short TTI
– Reduced delays
– Both 2 and 10 ms supported
§ Hybrid ARQ
– Fast retransmissions
– Soft combination of multiple attempts
§ Multi-code transmission
– 1-4 codes for E-DPDCH of SF 2/4
2/10 ms
Hybrid ARQ with
Soft Combining in RBS
TTI = 2 / 10 ms
Features
Multi-codetransmission
HSPA Basics
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 12
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0923
Signaling RB in 3GPP Release 6
E-DPDCH :t
ransits
the a
ctual d
ata
DPCCHHS-DPCCH
HS-PDSCH: t
ransm
its th
e actual d
ata
HS-SCCH
F-DPCH
E-DPCCH
E-HIC
HE-AGCH
HSPA Basics
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0924
HS-DSCH Data transmissionCompressed voice packet of 280 bits
Additional RLC UM OH of 8 bits
Additional MAC OH of typically 0+21 = 21 bits for voice packets
L1 CRC of 3 bytes (24 bits)L1
RLC SDU
L2 MAC-d
L2 RLC
3 bytes
L2 MAC-hs
Mapped onto HS-PDSCH(s) (1 TTI = 3 slots)
Transport Block (MAC-hs PDU, HARQ data block)
voice packet
RLCheader
1 bytes
MAC-dheader
RLC PDU
MAC-d PDU = MAC-hs SDU
…
…0 bits
MAC-hsheader
MAC-hs payload
RLC SDU
voice packet
RLCheader
MAC-dheader
RLC PDU
Typically
21 bits
Transport Block CRC
(Segmentation/Concatenation)
MAC-d PDU should be optimized for codecs used for MM Telephony to increase capacity. The number of PDU
sizes is limited to 8 (by a 3 bit field in the MAC-hs header)
HSPA Basics
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 13
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0925
Scheduling – A key challenge!
§ Real-time media – Continuously send small packets, avoid fading dips
– Scheduler that takes delay into account seems favorable
§ A well-tuned scheduler should optimize MM Telephony voice capacity but also not starve TCP
Node B
Scheduler
CQIFlow
charact.
RNC
HSPA Basics
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0926
Scheduling in general
Node BBuffers
§ Best effort traffic create large packets and possibility to buffer (and delay) packets
HSPA Basics
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 14
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0927
§ Real-time VoIP traffic create small delay sensitive packets
Node BBuffers
Voice capacity requires code
multiplexing
Scheduling in generalHSPA Basics
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0928
HSDPA Schedulers
§ Max CIR
§ PF
§ Delay scheduler
§ Barrier function example
( )maxi
iR
max i
ii
R
r
delay threshold
delay of first packet in buffer
th
i
d
d
=
=
1
( )i
th i
Bd d
=−
instantaneous possible bitrate
average offered bitrate
i
i
R
r
=
=
max ii
i
RB
r
⋅
HSPA Basics
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 15
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0929
Example of a delay scheduler
§ Based on e.g Proportional fair or Max C/I scheduler
§ Packets with high delay are given high priority
§ Packets with delay above threshold are dropped
§ Retransmissions automatically get priority
HSPA Basics
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0930
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
Outline
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 16
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0931
Assumptions and parameters
• Codec AMR 12.2 kbps
• Speech activity 50%
• ROHC yes
• Frames/packet 1
• Support small packets Code mux (4)
• Scheduler PF/Delay
• Hybrid ARQ yes
•Mobility yes (Poisson traffic)
• Channel HSDPA (DCH)
• Fading TU and Ped A
• Site to site distance 1500 m
• MS Antenna RX single
• Advanced receivers no
•
HSDPA
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0932
KPIs - User satisfaction & capacity
§ If packet loss ratio < 2 % user is satisfied– Ratio of packets delayed > max delay +
ratio of lost packets
§ 99% satisfied users in the system gives the maximum users per cell - the capacity
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 17
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0933
PF vs Delay scheduler
Capacity with delay scheduler is higher than for PF
Results
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0934
PF & RR vs Delay scheduler
Results
Re
lative
ca
pa
city
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 18
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0935
Delay threshold
Significant capacity reduction if delay budget decreases
Results
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0936
Channel
Capacity affected by radio channel
Results
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 19
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0937
Delay vs capacity
30
40
50
60
70
80
90
0 50 100 150 200 250
Delay [ms]
Nu
mb
er
of
users 1% loss
2% loss
Results
1.5
1
0.5
Re
lati
ve
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0938
Enables smooth migration from CS telephony to MM Telephony
§ Concurrent CS and PS voice users on the same carrier maintaining capacity
– MM Tel over HSPA use “remaining” power not used by CS
– No total voice capacity loss (rather the opposite!) when a part of the power budget is used by PS voice users
Ø Competitive advantage compared to CDMA 2000 EV-DO
0
0,2
0,4
0,6
0,8
1
1,2
1,4
20 18 16 14 12 10 8 6
VoIP
CS
CS + VoIP
Power reserved for CS traffic (W)
Rela
tive
Cap
acity
Results
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 20
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0939
VoIP over HSDPA CapacityResults
>10%
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0940
VoIP over EUL CapacityResults
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 21
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0941
Transport characteristics/qualitySummary of evaluations
§ IMS MMTel speech quality as good as CS speech
– Low jitter & fast RTT
– 220 ms or lower end-to-end latency
– No or low packet loss
End-to-end Application Layer Jitter Performance
-20
0
20
40
60
80
100
120
140
160
0 200 400 600 800 1000 1200 1400
Transmission Id Sorted according to PLR
De
lay
[m
se
c]
Delay min
Median
98 percentile
99 percentile
Results
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0942
§ All-IP or convergence
§ Mobile IP services
§ HSPA basics
§ Some examples of results
§ Why do we get the results we get?
Outline
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 22
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0943
Channel impactTCP benefits from ped A
VoIP capacity decided by the “worst”users!
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0944
Base station equations
Base station b
Mobile m
All other base stations n
,
target to get good quality
m b
m
CIR
g gain
orthogonality
γ
α
−
−
−
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 23
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0945
Base station equations CS capacity
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0946
Base station equations CS capacity
§ Solve for Ptot and simplify
§ Interference limited
§ Orthogonality and “F factor”or inverse of geometry factor
cP≈
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 24
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0947
Base station equations Channel variations
§ Orthogonality
§ Fast fading
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0948
Base station equations CS capacity
§ Simplify
§ Where
§ Mcs gives the number of CS voice users for a given Ptot=Pmax
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 25
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0949
PS over HSDPA capacitymodify base station equations
§ Modify (6) to fit for HSDPA and PS voice instead
§ Add HSDPA channels HS-SCCH and A-DPCH
§ We get:
Power of the CS users if any
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0950
PS over HSDPA capacitymodify base station equations
§ Note! Only C users transmitting data per TTI (=2ms)!
What about CIR target for HSDPA?
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 26
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0951
PS over HSDPA capacitymore about the channel variations
,,
,
1 ( 1)
hs scch adpch common
tot hs C Bm n
total mm bm n
CP MP PP
g
gγ α
− + +≈
− + −∑ ∑,m b
m
CIR
g gain
orthogonality
m mobiles
n cells
γ
α
−
−
−
−
−
Channel variations. DCH case: 0.6+0.8=1.4
,
1
hs scch adpch common
tot hs C
total worst
m
CP MP PP
γ φ
− + +≈
−∑
HS case: use “worst” user approach, =~4.5 for Typical Urban (6.0 for ped A)
φ
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0952
PS over HSDPA capacitythe HSDPA scheduler buffer - MAC hs buffer
§ Number of packets n at the MAC hs buffer:
1/ 2 / 20 1/10ms msλ = =%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
...Time [2ms TTI:s]
10 TTI:s = 20ms …….…….
10 TTI:s = 20ms …….
User 1
User 2…….
10 TTI:s = 20ms …….User 3…….
MAC hs buffer, user to be transmittedPacket
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 27
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0953
§ The required CIR γ is a function
of # packets to transmit each TTI
§ γ 320bits – required CIR to transmit
320 bits (~ AMR 12.2 kbps)
§ Rretx – number of transmissions
§ Round Robin assumed
320total total bits
total retx
n
Mn RC
γ γ
λ
= ⋅
= ⋅
RR – all users has the same number of packets in the buffer
PS over HSDPA capacity required CIR (1)
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0954
§ But what happens if there is not
enough power to transmit ntotal
packets?
§ Answer: Segmentation the ntotal
of into Rcoverage packets => extra
retransmissions!
§ Rcoverage – a model of the number
of possible (re)transmissions
with Dmax ms
§ The maximum delay at MAC-hs
buffer: Dmax ms
320
cov
320
max
2
320
max
total bitstotal
erage
total bits
total voip
total bits voip
n
R
n
D
n T
n T
D
γγ
γ
γ
⋅=
⋅=
⋅
⋅ ⋅=
PS over HSDPA capacity required CIR (2) – maximum delay
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 28
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0955
PS over HSDPA capacity add CIR to base station equation
( )
( ) ( )
( )
, max,
max,
2320 max,
max
max, max
1
1 /
1 /
1 /
hs scch commontot hs hs C
total worst
m
Chs scch common hs
totalworstm
Cbits voip hs scch common hs
retxworstm
hs scch common hs
wo
CP PP P
CP P P
T CP P PM RC D
CP P P C DM
γ φ
γφ
γλφ
φ
−
−
−
−
+= ≈
−
− +=
⋅ − +⋅ =
− + ⋅ =
∑
∑
∑
( )2
320rst retx bits voipMR Tλ γ ⋅
Theory etc
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0956
Theoretical VoIP capacitygives answer to the “why”?
§ Capacity is ~ sqrt(delay )
§ Activity (packet arrival) λ –
linear vs capacity
§ Required CIR is 1/sqrt(γ 320bits)
( )
( )max, max
2
320
1 /hs scch common hs
worst retx bits voip
CP P P C DM
MR Tφ λ γ
− − + ⋅ ≈⋅
Theory etc
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 29
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0957
Delay vs capacity
§Delay is sqrt(Dmax ) ~ capacity
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0958
Rx diversity vs capacity
§Required CIR is 1/sqrt(γ 320bits)
Providing efficient and reliable multimedia telephony over HSPA
2006-05-09
Ericsson AB 2006 30
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0959
Technology challenges - summary
Some have been solved but work remains:– How to trade delay, capacity and coverage appropriately– Small payloads – low bit rate– Scheduling– Signaling channels– Efficient radio bearer– Reduction of IP related overhead – Low latency and round trip time– End-to-end service assurance– Service differentiation– Speech / conversational quality and handling of jitter– Session setup– Voice as part of a multimedia scenario as well as stand-alone– Coverage
© Ericsson AB 2006 Ericsson Confidential Providing efficient and reliable multimedia telephony over HSPA 2006-05-0960
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