1. Wireless IP Multimedia
Henning Schulzrinne
Columbia University
MOBICOM Tutorial, September 2002

2. Overview Header and signaling compression Packet FEC
Types of wireless multimedia applications
streaming
interactive
object delivery
Properties of multimedia content
loss resiliency
delay
reordering
3G and WLAN MM-related channel properties
effective bandwidth
packet loss
Header and signaling compression
cRTP
ROHC
signaling compression
Packet FEC
UMTS multimedia subsystem (IMS)
QoS
Session setup
Fast handoff mechanisms
Multimodal networking
23 April 2017

3. Types of wireless multimedia applications
Interactive
VoIP
multimedia conferences
multiplayer games
Streaming
video/audio on demand
broadcast TV/radio
may be cached at various places, including end system
Object retrieval
peer-to-peer
user may be waiting for result
Messaging
store-and-forward (e.g., MMS)
can be batched
23 April 2017

4. IETF (multimedia) protocols
Media Transport
media encap
(H.261. MPEG)
Signaling
SAP
SDP
MGCP
DHCPP
H.323
SIP
RTSP
RSVP
RTCP
DNS
RTP
LDAP
Application
TCP
UDP
CIP
IDMP
MIPv6
Network
MIP
MIP-LR
IPv4, IPv6, IP Multicast
ICMP
IGMP
Kernel
PPP
AAL3/4
AAL5
PPP
Physical
CDMA 1XRTT
/GPRS
SONET
ATM
802.11b
Ethernet
Heterogeneous
Access
23 April 2017

5. Common wired & wireless audio codecs
codec name
standards org.
sampling rate (Hz)
frame size
bit rate (kb/s)
G.711 (µ/A-law)
ITU
8,000
any 64
G.723.1
20 ms
5.3, 6.3
G.729 (CS-ACELP)
ITU (1996)
10 ms 8
AMR
(adaptive multi-rate)
ETSI
(1999)
4.75 – 12.2 (8)
6.7: PDC-EFR
7.4: IS 641
12.2: GSM-EFR
GSM-HR
GSM 06.20
5.6
GSM-FR
GSM 06.10 13
AMR-WB (wideband)
ETSI
16,000
6.6 – (9)
23 April 2017

6. Audio codecs, cont'd. codec name standards org. frame size
sampling rate (Hz)
frame size
bit rate (kb/s)
EVRC (RCELP)
TIA/EIA (1996)
8,000
20 ms
8.55, 4, 0.8
G.726 (ADPCM)
ITU
sample
16, 24, 32, 40
G.728 (LD-CELP) 16
23 April 2017

7. Audio codecs
MP3 and AAC: delay > 300 ms  unsuitable for interactive applications
GSM and AMR are speech (voiceband) codecs  3.4 kHz analog designed for circuit networks with non-zero BER
Wideband = split into two bands, code separately  conferencing
AMR is not variable-rate (dependent on speech content)
receiver sends Codec Mode Request (CMR) to request different codec, piggy-backed on reverse direction
trade-off codec vs. error correction
23 April 2017

8. Audio codecs
Typically, have algorithmic look-ahead of about 5 ms  additional delay
G.728 has ms look-ahead
AMR complexity: MIPS, 5.3 KB RAM
original 4 6 8 10 12 14 16 18 20 22 24
G.723.1
G.729
G.729A
AMR-NB
AMR-WB
23 April 2017

9. Audio codecs - silence
Almost all audio codecs support Voice Activity Detection (VAD) + comfort noise (CN)
comfort noise: rough approximation in energy and spectrum  avoid "dead line" effect
G.729B
AMR built-in: CN periodically in Silence Indicator (SID) frames = discontinuous transmission (DTX)  saves battery power
or source controlled rate (SCR)
23 April 2017

10. Audio codecs - silence silence periods depend on
background noise
word vs. sentence vs. alternate speaker
particularly useful for conferences
small ratio of speakers to participants
avoid additive background noise
23 April 2017

11. Video codecs JPEG MPEG, H.26x common code words  shorter symbols
Huffman, arithmetic coding
e.g., DCT:
spatial  frequency
Motion
Estimation
&
Compensation
Transform,
Quantization, Zig-
Zag Scan & Run-
Length Encoding
Symbol
Encoder
Frames of
Digital Video
Bit Stream
predict current
frame from previous
Quantization changes representation
size for each symbol
adjust rate/quality trade-off
Run-length encoding:
long runs of zeros  run-length symbol
courtesy
M. Khansari
MPEG, H.26x
23 April 2017

12. History of video codecs
ITU-T
H.263+
H.263L
MPEG 1
MPEG 4
ISO
MPEG 2
MPEG 7
1990
1992
1994
1996
1998
2000
2002
courtesy
M. Khansari
23 April 2017

13. H.263L example
64 kb/s, 15 fps
courtesy of Siemens CT
23 April 2017

14. Delay requirements In many cases, channel is delay constrained:
ARQ mechanisms
FEC
low bandwidths
ITU G.114 Recommendation:
ms one way delay: acceptable to most users
ms: acceptable with impairments
Other limits:
telnet/ssh limit ~ ms [Shneiderman 1984, Long 1976]?
reaction time 1-2 s for human in loop [Miller 1968]:
web browser response
VCR control for streaming media
ringback delay for call setup
can often be bridged by application design
23 April 2017

15. 802.11 architecture ESS Existing Wired LAN AP AP STA STA STA STA BSS
Infrastructure Network
STA
STA
Ad Hoc Network
Ad Hoc Network
BSS
BSS
STA
STA
Mustafa Ergen
23 April 2017

16. 802.11b hand-off
Kanter, Maguire, Escudero-Pascual, 2001
23 April 2017

17. 802.11 delay channel idle is busy Data ACK slots idle slots time DIFS
SIFS
DIFS
(DCF interframe space)
(short IFS)
idle
idle
RTS CTS Data ACK
slots
slots
time
DIFS
SIFS
SIFS
SIFS
DIFS
IFS (µs)
FHSS
DSSS
OFDM
SIFS 28 10 13
PIFS 78 30 19
DIFS
128 50 25
M. Zukerman
23 April 2017

18. 802.11 delay 802.11b: 192 bit PHY headers  192 µs (sent at 1 Mb/s)
DSSS
802.11b
11 Mb/s
FHSS, DSSS
802.11a
2, 11, 24, 54 Mb/s
OFDM
802.11b: 192 bit PHY headers  192 µs (sent at 1 Mb/s)
802.11a: 60 µs
three MAC modes:
DCF
DCF + RTS
PCF: AP-mode only
23 April 2017

19. delay
23 April 2017

20. delay
23 April 2017

21. 802.11a delay for VoIP
23 April 2017

22. 802.11b channel access delay
Köpsel/Wolisz
12 mobile data nodes, 4 mobile with on/off audio
6 Mb/s load
23 April 2017

23. 802.11b VoIP delay
Köpsel/Wolisz WoWMoM 2001: add priority and PCF enhancement to improve voice delay
DCF
Köpsel/Wolisz
23 April 2017

24. 802.11b – PCF+priority poll only stations with audio data
move audio flows from PCF to DCF and back after talkspurts
Köpsel/Wolisz
IEEE TGe working on enhancements for MAC (PCF and DCF)
multiple priority queues
23 April 2017

25. 802.11e = enhanced DCF HC hybrid controller TC traffic categories AIFS
arbitration IFS
TXOP
transmission opportunity
Mustafa Ergen
23 April 2017

26. 802.11e back-off
23 April 2017

27. Metric of VoIP quality Mean Opinion Score (MOS) [ITU P.830]
Obtained via human-based listening tests
Listening (MOS) vs. conversational (MOSc)
Grade
Quality 5
Excellent 4
Good 3
Fair 2
Poor 1
Bad
23 April 2017

28. FEC and IP header overhead
An (n,k) FEC code has (n-k)/k overhead
Typical IP/UDP/RTP header is 40 bytes
codec
media pkt size (T=30ms)
rmedia
rIP
iLBC
(4,2) FEC
54 bytes
14.4 kb/s
25.1 kb/s
108 bytes
28.8 kb/s
39.5 kb/s
G.729
30 bytes
8 kb/s
18.7 kb/s
60 bytes
16 kb/s
26.7 kb/s
G.723.1
24 bytes
6.4 kb/s
17.1 kb/s
48 bytes
12.8 kb/s
23.5 kb/s
23 April 2017

29. Predicting MOS in VoIP
The E-model: an alternative to human-based MOS estimation
Do need a first-time calibration from an existing human MOS-loss curve
In VoIP, the E-model simplifies to two main factors: loss (Ie) and delay (Id)
A gross score R is computed and translated to MOS.
Loss-to-Ie mapping is codec-dependent and calibrated
23 April 2017

30. Predicting MOS in VoIP, contd
Example mappings
From loss and delay to their impairment scores and to MOS
23 April 2017

31. Predicting MOS under FEC
Compute final loss probability pf after FEC [Frossard 2001]
Bursty loss reduces FEC performance
Increasing the packet interval T makes FEC more efficient under bursty loss [Jiang 2002]
Plug pf into the calibrated loss-to-Ie mapping
FEC delay is n*T for an (n,k) code
Compute R value and translate to MOS
23 April 2017

32. Quality Evaluation of FEC vs. Codec Robustness
Codecs under evaluation
iLBC: a recent loss-robust codec proposed in IETF; frame-independent coding
G.729: a near toll quality ITU codec
G.723.1: an ITU codec with even lower bit-rate, but also slightly lower quality.
Utilize MOS curves from IETF presentations for FEC MOS estimation
Assume some loss burstiness (conditional loss probability of 30%)
Default packet interval T = 30ms
23 April 2017

33. G.729+(5,3) FEC vs. iLBC
Ignoring delay effect, a larger T improves FEC efficiency and its quality
When considering delay, however, using a 60ms interval is overkill, due to higher FEC delay (5*60 = 300ms)
23 April 2017

34. G.729+(5,2) vs. iLBC+(3,2)
When iLBC also uses FEC, and still keeping similar gross bit-rate
G.729 still better, except for low loss conditions when considering delay
23 April 2017

35. G.729+(7,2) vs. iLBC+(4,2) Too much FEC redundancy (e.g., for G.729)
 very long FEC block and delay
 not always a good idea
iLBC wins in this case, when considering delay
23 April 2017

36. G.729+(3,1) vs. iLBC+(4,2)
Using less FEC redundancy may actually help, if the FEC block is shorter
Now G.729 performs similar to iLBC
23 April 2017

37. Comparison with G.723.1 MOS(G.723.1) < MOS(iLBC) at zero loss
 iLBC dominates more low loss areas compared with G.729, whether delay is considered or not
23 April 2017

38. G.723.1+(3,1) vs. iLBC+(3,2) iLBC is still better for low loss
G wins for higher loss
23 April 2017

39. G (4,1) vs. iLBC+(4,2)
iLBC dominates in this case whether delay is considered or not,
(4,2) code already suffices for iLBC
(4,1) code’s performance essentially “saturates”
23 April 2017

40. The best of both worlds Observations, when considering delay:
iLBC is usually preferred in low loss conditions
G.729 or G FEC better for high loss
Example: max bandwidth 14 kb/s
Consider delay impairment (use MOSc)
23 April 2017

41. Max Bandwidth: kb/s
23 April 2017

42. Effect of max bandwidth on achievable quality
14 to 21 kb/s: significant improvement in MOSc
From 21 to 28 kb/s: marginal change due to increasing delay impairment by FEC
23 April 2017

43. UMTS and 3G wireless Staged roll-out with "vintages"  releases:
Release 3 ("1999")  GPRS data services
Multimedia messaging service (MMS) = SMS successor ~ MIME
RAN via evolved CDMA
Release 4: March 2001
Release 5: March-June 2002
Release 6: June 2003  all-IP network
Main future new features (affecting packet services):
All-IP transport in the Radio Access and Core Networks
Enhancements of services and service management
High-speed Downlink Packet Access (HSDPA)
Introduces additional downlink channels:
High-Speed Downlink Shared Channel (HS-DSCH)
Shared Control Channels for HS-DSCH
23 April 2017

44. UMTS macrocell 2 km 144 kb/s microcell 1 km 384 kb/s picocell 60 m
2 Mb/s
Follow-on to GSM, but WCDMA physical layer
new ($$$) spectrum around 2 GHz
radio transmission modes:
frequency division duplex (FDD): 2 x 60 MHz
time division duplex (TDD): MHz
Chip rate 3.84 Mcps  channel bandwidth 4.4 – 5 MHz
23 April 2017

45. 1G-3G air interface 1G 2G “2.5G” 3G/ IMT-2000 Capable
Existing Spectrum New Spectrum
cdma2000 1X (1.25 MHz)
cdma2000 3X (5 MHz)
Analog
AMPS
IS-95-A/
cdmaOne
IS-95-B/
cdmaOne
1XEV DO: HDR (1.25 MHz)
IS-136
TDMA
136 HS
EDGE
TACS
GSM GPRS
EDGE
GSM
HSCSD
WCDMA
23 April 2017
Ramjee

46. The mysterious 4G Fixes everything that's wrong with 3G 
Convergence to IP model: treat radio access as link layer that carries IP(v6) packets
not necessarily new radio channel
no new spectrum available
all-IP radio access network (RAN)
common mobility management
AAA and roaming
user identifiers
roaming across wired networks
23 April 2017

47. UMTS – 3GPP and 3GGP2 Divided regionally/historically:
both from ITU IMT-2000 initiative
GSM  3GPP (ETSI) = WCDMA
US (CDMA)  3gpp2 (TIA) = CDMA2000
3GPP2: different PHY, but similar applications (not completely specified)
cdma2000
23 April 2017

48. UMTS
W. Granzow
23 April 2017

49. 3GPP network architectureAS
23 April 2017
Jalava

50. 3GPP network architecture - gateways
Legacy Mobile
Signaling Networks
Multimedia
IP Networks
Roaming Signaling Gateway (R-SGW) Mm Mh Ms
HSS
CSCF Gi Cx Mg Mr Gi
MRF
Media Gateway Control Function (MGCF)
Transport Switching Gateway (T-SGW)
SGSN
GGSN Gi
Mc (= H.248)
PSTN/Legacy/External
Media Gateway (MGW)
Media Gateway (MGW) Gi
23 April 2017
Alves

51. 3GPP networks – call control
-View on CALL CONTROL -
Applications & Services
VHE / OSA
Application I/F
CAP
Call State Control Function (CSCF)
Home Subscriber Server (HSS)
(=HLR + +) Cx Mr
Multimedia Resource Function (MRF) Gc Gi Gr Gi
SGSN
GGSN
access Gn
to other networks Iu Gf
EIR
23 April 2017
Alves

52. UMTS network architecture
MSC Mobile Services Switching Center
GSN GPRS Support Node
MSC/GSN
Node B
RNC
RNC Radio Network controller
Node B Base Node
Radio network
System (RNS)
Node B
23 April 2017
W. Granzow

53. Aside: some 3G/UMTS terminologyCS
circuit-switched
GERAN
GSM/EDGE Radio Access Network
GGSN
Gateway GPRS Support Node. A router between the GPRS network and an external network (i.e., the Internet).
PDP
Packet Data Protocol
PDP context
A PDP connection between the UE and the GGSN. PS
packet-switched
SGSN
Serving GPRS Support Node
UTRAN
Universal Terrestrial Radio Access Network
See RFC 3114 for brief introduction.
23 April 2017

54. UTRA transport channels categories
Common channels
Multiplexed users (user ID in the MAC header)
Forward Access Channel (FACH)
Random Access Channel (RACH)
Common Packet Channel (CPCH)
Dedicated channels (DCH)
Assigned to a single user (identified by the spreading code)
Shared channels
„Sharing“ of code resource by several users by fast re-assignment scheduling
Downlink Shared Channel (DSCH)
23 April 2017

55. Transmission Format UTRA FDD
1 radio frame (10 ms), 15*2560 chips (3.84 Mcps)
Slot i
Slot 1
Slot 2
Slot 15
time
frequency
5 MHz
Macrocell layers
Microcell
layer
Duplex distance, e.g. 190 MHz
Uplink
Downlink
23 April 2017

56. UMTS/3G QoS classes conversational voice, video conferencing
low delay, strict ordering
streaming
video streaming
modest delay, strict ordering
interactive
web browsing, games
modest delay
background
download
no delay guarantees
23 April 2017

57. QoS class requirements
Excerpt from 3GPP TS :
Traffic class
Conversational
Streaming
Interactive
Background
Residual BER
5*10-2, 10-2, 5*10-3, 10-3, 10-4, 10-6
5*10-2, 10-2, 5*10-3, 10-3, 10-4, 10-5, 10-6
4*10-3, 10-5, 6*10-8
SDU error rate
10-2, 7*10-3, 10-3, 10-4, 10-5
10-1, 10-2, 7*10-3, 10-3, 10-4, 10-5
10-3, 10-4, 10-6
10-3, 10-4,
10-6
Transfer delay
 100 ms
 250 ms
Guaranteed bit rate
2,048 kb/s
Traffic handling priority
1,2,3
Allocation/retention priority
23 April 2017

58. GPRS delay
Gurtov, PWC 2001
23 April 2017

59. UMTS transport
23 April 2017

60. UMTS Release 4/5 Architecture
Kulkarni
23 April 2017

61. QoS in UMTS
Short term: signaling  tell network elements about QoS requirements
RSVP (IntServ)
DiffServ with DSCPs
PDP context
Longer term: provisioning  allocate resources to QoS classes
low network utilization (overprovisioning)
DiffServ
IntServ (possibly for DiffServ classes, RFC xxxx)
MPLS
Mechanisms can be heterogeneous
DSCP translation
localized RSVP
23 April 2017

62. QoS signaling in UMTS UMTS R5: two end-to-end QoS signaling scenarios
QoS provisioning left vague
RSVP currently not in standard
additional scenario featuring RSVP may be added to a later release of the standard
QoS connected to application layer signaling (SIP) SIP - Session Initiation Protocol
necessary for IP telephony, not streaming or data
SIP allows applications to agree on address, port, codec, ...
standardized by IETF
but UMTS-specific SIP dialect
additional functionality compared to IETF SIP
23 April 2017

63. Session setup: SIP INVITE REGISTER BYE 23 April 2017
INVITE SIP/2.0
Via: SIP/2.0/UDP pc33.atlanta.com
;branch=z9
Max-Forwards: 70
To: Bob
From: Alice
;tag=
Call-ID:
CSeq: INVITE
Contact:
Content-Type: application/sdp
Content-Length: 142
REGISTER
BYE
23 April 2017

64. Session setup: SIP Creates, modifies, terminates sessions
sessions = audio, video, text messages, …
IETF RFC
UTF-8 text, similar to HTTP
request line
headers
body (= session description ~ SDP), not touched by proxies
URLs for addresses
tel:
Client 1
Client 2
INVITE
INVITE
100 Trying
180 Ringing
180 Ringing
200 OK
200 OK
ACK
ACK
Media streams
BYE
BYE
200 OK
200 OK
Jalava
23 April 2017

65. SIP request routing SIP proxies route all SIP requests
don't care about method (INVITE, REGISTER, DESTROY, …)
use location server based on registrations
e.g., 
route to one or more destinations
parallel forking
sequential forking
use Via header to track proxies visited  loop prevention
normally, only during first request in dialog
but proxy can request visits on subsequent requests via Record-Route
user agent copies into Route header
also used for service routing  preloaded routes
23 April 2017

66. 3GGP Internet Multimedia Subsystem
services (call filtering, follow-me, …) provided in home network, via Home Subscriber Server (HSS)
may use CAMEL for providing services, but also
Call Processing Language (CPL)
SIP Common Gateway Interface (sip-cgi, RFC 3050)
SIP Servlets (JAIN)
VoiceXML for voice interaction (IVR)
use ENUM (DNS) to map E.164 numbers to SIP URIs
becomes e164.arpa
mechanisms and roles:
proxy servers  call routing, forking
user agents (UA)  voice mail, conferencing, IM
back-to-back UA (B2BUA)  3rd party call control
23 April 2017

67. UMTS IP multimedia
23 April 2017

68. IMS session overview
23 April 2017
Jalava

69. 3GPP Internet Multimedia Subsystem
Call State Control Function (CSCF)
Home
Application
Server
Subscriber
Subscription
Server
Interrogating-CSCF
Location Function Sh
Accesspoint to domain
Hides topology and configuration
SLF
HSS AS
Diameter
Diameter
ISC UE Dx Cx Cx
SIP Gm Mw Mw UA
P-CSCF
I-CSCF
S-CSCF
(User Agent)
SIP
SIP
SIP
Visited
Domain
Home
Domain
Serving-CSCF
Proxy-CSCF
Session control services
Registration, AS usage, charging, etc
23 April 2017
Jalava

70. Locating the P-CSCF
2 mechanisms:
23 April 2017

71. 3GPP SIP registration sip:23415098765@15.234.IMSI.3gppnetwork.org
TS /5.1
23 April 2017

72. 3GPP IMS call setup
23 April 2017

73. IMS call setup with QoS
23 April 2017

74. SIP for mobility Terminal mobility Personal mobility Service mobility
same device, different attachment point
nomadic/roaming user: change between sessions
mid-session mobility
Personal mobility
same person, multiple devices
identified by SIP address-of-record
Service mobility
configuration information
address book, speed dial, caller preferences, …
Session mobility
hand-over active session to different device
e.g., cell phone to office PC
23 April 2017

75. SIP for terminal mobility
For most UDP applications, no need to keep constant source IP address at CH
e.g., RTP uses SSRC to identify session
others typically single request-response (DNS)
TCP: see Dutta et al. (NATs, proxies) or Snoeren/Balakrishnan TCP migration CH
REGISTER IP1
registrar
INVITE
re-INVITE
IP2
REGISTER IP2
23 April 2017

76. SIP mobility vs. mobile IP
Mobility at different layers:
permanent identifier
rendezvous point identified by that identifier
forwarding of messages
mobile IP
SIP
permanent identifier
IP address
SIP AOR
temporary address
care-of-address
Contact header
rendezvous point
home agent ( permanent address)
registrar ( host part of AOR)
HA/FA discovery
ICMP
not needed (name)
binding update
UDP message
REGISTER
in visited network
foreign agent (FA)
none/outbound proxy
23 April 2017

77. SIP hierarchical registration1
From:
Contact: 2
From:
Contact: CA NY
San Francisco
registrar 4
proxy
From:
Contact: 3
REGISTER
INVITE
Los Angeles
23 April 2017

78. SIP personal mobility
23 April 2017

79. 3GPP – IETF SIP differences
SIP terminal + authentication = 3GPP terminal
signaling as covert channel?  death of SMS?
CSCFs are not quite proxies, not quite B2BUAs
modify or strip headers
initiate commands (de-registration, BYE)
edit SDP  violate end-to-end encryption
modify To/From headers
23 April 2017

80. NSIS = Next Steps in Signaling
IETF WG to explore alternatives (or profiles?) of RSVP
currently, mostly requirements and frameworks
RSVP complexity  multicast support
forwarding state
killer reservations
receiver orientation not always helpful
better support for mobility
pre-reserve
tear down old reservations
layered model (Braden/Lindell, CASP)
signaling base layer, possibly on reliable transport (CASP)
applications/clients, e.g., for resources, firewall, active networks
proposals:
trim RSVP
CASP (Cross-Application Signaling Protocol) Columbia/Siemens
23 April 2017

81. Header compression Wireless access networks =
high latency: ms
bit errors: 10-3, sometimes 10-2
non-trivial residual BER
low bandwidth
IP  high overhead compared with specialized circuit-switched applications:
speech frame of octets
IPv4+UDP+RTP = 40 bytes of header, 60 with IPv6
SIP session setup ~ 1000 bytes
23 April 2017

82. Header compression 3GPP architecture 23 April 2017
3GPP Architecture for all IP networks
23 April 2017

83. Header compression
Pure use of dictionary-based compression (LZ, gzip) not sufficient
Similar to video/audio coding  remove "spatial" and "temporal" redundancy
Usually, within some kind of "session"
Access network (one IP hop) only
Layering violation: view IP, UDP, RTP as whole
see also A Unified Header Compression Framework for Low-Bandwidth Links, Lilley/Yang/Balakrishnan/Seshan, Mobicom 2000
23 April 2017

84. Compressed RTP (CRTP)
VJ header compression for TCP  uses TCP-level retransmissions to updated decompressor
RFC 2508: First attempt at RTP header compression
2 octets without UDP checksum, 4 with
explicit signaling messages (CONTEXT_STATE)
out-of-sync during round trip time  packet loss due to wrong/unknown headers
Improvement: TWICE
if packet loss  decompressor state out of sync
use counter in CRTP to guess based on last known packet + verify using UDP checksum
only works with UDP checksum  at least 4 octets
23 April 2017

85. Robust header compression (ROHC)
Avoid use of UDP checksums
most speech codecs tolerate bit errors
not very strong 
payload errors cause spurious header prediction failures
may accept wrong header
Loss before compression point may make compressed RTP header behavior less regular
100 ms of loss exceeds loss compensation ability
ROHC: primarily for RTP streams
header field = f(RTP seq. no)
communicate RTP seq. no reliably
if prediction incorrect, send additional information
23 April 2017

86. ROHC Channel assumptions: Negotiated via PPP
does not reorder (but may before compressor)
does not duplicate packets
Negotiated via PPP
ROHC profiles: uncompressed, main (RTP), UDP only, ESP only
Initialization
and Refresh
First Order
Second Order
23 April 2017

87. Header classification
inferred
can be deduced from other values (e.g., length of frame)
not transmitted
static
constant through lifetime of packet stream
communicate once
static-def
values define packet stream
like static
static-known
well-known values
changing
randomly or within range
compress by 1st/2nd order "differentiation"
23 April 2017

88. Example: IPv6 Field Size (bits) type Version 4 static Traffic Class 8
changing
Flow Label 20
static-def
Payload Length 16
inferred
Next Header
Hop Limit
Src/Dest address
2x128
inferred 2
static
1.5
static-def
34.5
changing
23 April 2017

89. Example: RTP Field Size (bits) type Version 2 static-known Padding 1
Extension
CSRC Counter, Marker, PT 12
changing
Sequence Number 16
Timestamp 32
SSRC
static-def
CSRC
0(-480)
inferred
2 bits
static-def 4
static-known
changing
7.5 (-67.5)
23 April 2017

90. Behavior of changing fields
static
additional assumptions for multimedia
semi-static
occasionally changes, then reverts
rarely changing (RC)
change, then stay the same
alternating
small number of values
irregular
no pattern
23 April 2017

91. Classification of changing fields
Value/Delta
Class
Knowledge
IP TOS/Traffic Class
value RC
unknown
IP TTL / Hop Limit
alternating
limited
UDP checksum
irregular
RTP CSRC, no mix
static
known
RTP CSRC, mix
RTP marker
semi-static
RTP PT
RTP sequence number
delta
RTP timestamp
23 April 2017

92. ROHC modes Unidirectional (U) Bidirectional Optimistic (O)
compressor  decompressor only
periodic timeouts only
starting state for all modes
Bidirectional Optimistic (O)
feedback channel for error recovery requests
optional acknowledgements of significant context updates
Bidirectional Reliable (R)
more intensive usage of feedback channel
feedback for all context updates
23 April 2017

93. ROHC encoding methods Least significant bits (LSB)
header fields with small changes
k least significant bits
interpretation interval
f(vref,k) = [vref – p, vref + (2k –1) – p]
p picked depending on bias of header field
window-based LSB (W-LSB)
compressor maintains candidates for decompressor reference value
23 April 2017

94. ROHC encoding methods, cont'd
Scaled RTP timestamp encoding
RTP increases by multiple of TS_STRIDE
e.g., 20 ms frames  TS_STRIDE=160
downscale by TS_STRIDE, then W-LSB
Timer-based compression of RTP timestamp
local clock can provide estimate of TS
if jitter is bounded
works well after talkspurts
Offset IP-ID encoding
compress (IP-ID – RTP SN)
Self-describing variable length encoding
prefix coding: 0 + 1o, o, o, o
23 April 2017

95. ROHC typically, multiple streams for each channel
duplicate,
reorder, lose
packets
compressor
de-
compressor
ACK
NACK
typically, multiple streams for each channel
identified by channel identifier (CID)
protected by 3-8 bit CRC
23 April 2017

96. ROHC CRC Qiao: add one-bit correction CRC helps with BER of 4-5%
Full header
CRC
Compressed header
Decompressed header
Validate
Qiao
23 April 2017

97. Signaling compression (SigComp)
Textual signaling protocols like SIP, RTSP and maybe HTTP
long signaling messages ( kB)
signaling delays  call setup delays (56 ms/1 144 kb/s)
less of an issue: total overhead
long packets  header overhead not a major issue
unlike ROHC, assume reliable transport
SigComp
ROHC
SIP
proxy
23 April 2017

98. Signaling compression
application message
& compartment id
decompressed
message
compartment
identifier
compressor
dispatcher
decompressor
dispatcher
state
handler
compressor 1
state 1
de-
compressor
(UDVM)
SigComp
message
SigComp
message
compressor 2
state 2
SigComp
layer
transport layer (TCP, UDP, SCTP)
23 April 2017

99. SigComp
Messages marked with special invalid UTF-8 bit sequence (11111xxx)
State saved across messages in compartment
memory size is limited (> 2 KB)
CPU expenditure is limited, measured in cycles per bit
Universal Decompressor Virtual Machine (UDVM):
compressor can choose any algorithm to compress
upload byte code as state
23 April 2017

100. request state information
SigComp UDVM bytecode
virtual machine with registers and stack
single byte opcode + literal, reference, multitype and address
request compressed data
UDVM
decompressor
dispatcher
provide compressed data
output decompressed data
indicate end of message
provide compartment identifier
request state information
state
handler
provide state information
make state creation request
forward feedback information
23 April 2017

101. SigComp virtual machine
arithmetic: and, or, not, left/right shift, integer add/subtract/multiply/divide, remainder on 16-bit words
sort 16-bit words ascending/descending
SHA-1, CRC
load, multiload, copy, memset, push, pop
jump, call, return, switch
input, output
state create and free
23 April 2017

102. Example: SIP compression
SIP compression most likely will use a static dictionary
e.g., "sip:", "INVITE ", "[CRLF]Via: SIP/2.0/UDP "
referenced as state
works best with default-formatted messages (e.g., single space between : and header field)
permanently defined
used with a variety of algorithms, such as DEFLATE, LZ78, …
Capability indicated using NAPTR records and REGISTER parameter
;; order pref flags service regexp replacement
IN NAPTR "s" "SIP+D2T" "" _sip._tcp.school.edu
IN NAPTR "s" "SIP+D2U" "" _sip._udp.example.com
IN NAPTR "s" "SIP+D2CU" "" comp-udp.example.com
23 April 2017

103. RTP unequal error protection
Provide generic protection of RTP headers and payload against packet loss
may also handle uncorrected bit errors
RFC 2733: XOR across packets  FEC packet
ULP (uneven level protection): higher protection for bits at beginning of packet
higher protection = smaller group sizes
common for most codecs: closer to sync marker
H.263: video macroblock header, motion vectors
modern audio codecs
stretching of existing audio codecs
23 April 2017

104. RTP unequal error protection
RTP seq. number base
length recovery E
PT recovery
bit mask (packets after SN base)
RTP timestamp recovery
separate FEC packets or piggy-backed
multiple FEC in one packet
ULP header adds protection length and mask
recovery bytes are XOR(packet headers)
negotiated via SDP
23 April 2017

105. Unequal erasure protection (UXP)
Alternative to ULP, with different properties
uses interleaving + Reed-Solomon codes (GF(28)) to recover from packet loss (erasure)
allows unequal protection of different parts of payload
allows arbitrary packet size  optimize for channel
interleaving adds delay
ULP only incurs delay after packet loss (but this may introduce gaps)
23 April 2017

106. UDPLite Proposal by Larzon&Degermark partial checksum coverage
at least UDP header bytes
source port
destination port
checksum coverage
UDP checksum
data bytes
23 April 2017

107. Fast handoff – hand-off latency
Allow only a few lost packets  < 100 ms hand-off delay
detect new network from AP MAC address
maybe use other packets listened to?
scan different frequencies
may need to scan both 2.4 and 5 GHz regions (802.11a, b, g)
passive scanning: wait for AP beacon
beacon interval = 100 kµs ~ 100 ms
active scanning: Probe Request Frame + Probe Response
associate with new network
802.11i authentication
IETF PANA WG – L2-independent access control
23 April 2017

108. Handoff latency duplicate address detection (DAD)
DHCP
DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK  multiple RTT, plus possible retransmissions
IPv6 stateless autoconfiguration (RFC 2461, 2462)
delay first Neighbor Solicitation in [0,MAX_RTR_SOLICITATION_DELAY], where MAX_RTR_SOLICITATION_DELAY = 1s
wait for RetransTimer (1s) for answer
AAA (authentication, authorization, accounting)
usually, RADIUS or (future) DIAMETER
server may be far away
23 April 2017

109. Castelluccia/Bellier
MIPv6 delays
Internet
Internet HA 2 2 CH
BU=
HA, CoA
BU=
HA, CoA 1 3 1
Site1
Site1
CoA
Castelluccia/Bellier
23 April 2017

110. Micro-mobility
Separate local (intra-domain, frequent) movement from inter-domain movement (rare)
 3 mobility protocol layers: L2 (e.g., , 3G RAN), micro, macro
also offer paging (usefulness with chatty UEs?)
assumption may not be correct
Examples:
hierarchical foreign agents (Nokia, 1996)
Cellular IP (Columbia/Ericsson, 1998)
Hierarchical IPv6 (INRIA, 1998)
HAWAII (Lucent, 1999)
THEMA (Lucent/Nokia, 1999)
TeleMIP (Telcordia, IBM, 2001)
ISP1
ISP2
100'
23 April 2017

111. Micro-mobility design goals
Scalability
process updates locally
Limit disruption
forward packets if necessary
Efficiency
avoid tunneling where possible
Quality of Service (QoS) support
local restoration of reservations
Reliability
leverage fault detection mechanisms in routing protocols
Transparency
minimal impact at the mobile host
23 April 2017
Ramjee

112. Micro-mobility Methods based on re-addressing Routing-based
"keep routes, change address"
typically, tunnels within domain
hierarchical FAs
MIP with CoA to world at large
e.g.,
regional registration, region-aware foreign agents, Dynamics, hierarchical MIPv6, …
Routing-based
"keep address, change routes"
no tunnels within domain
host-based (mobile-specific) routes
Cellular IP, HAWAII
23 April 2017
Hartenstein et al.

113. Cellular IP
23 April 2017

114. Cellular IP base station routes IP routes  cellular IP routing
gateway support MIP macro mobility
provides CoA
inside micro mobility domain, packets identified by
no tunneling, no address conversion
MH data packets establish location and routing "soft state"
no explicit signaling
empty IP packets
discarded at border
symmetric paths
uplink establishes shortest path to MH
per-host routes, hop-by-hop
Gomez/Campbell
23 April 2017

115. Cellular IP: Hard handoff
Internet w/ Mobile IP
foreign agent
home agent C A B E D F G R
host
Gomez/Campbell
23 April 2017

116. Cellular IP: downlink HO loss
23 April 2017

117. HAWAII: Enhanced Mobile IP
Internet
Domain
Router
Domain
Router R R R R R R R R MD
Local mobility
Local mobility
Mobile IP
Distributed control: Reliability and scalability
host-based routing entries in routers on path to mobile
Localized mobility management: Fast handoffs
updates only reach routers affected by movement
Minimized or Eliminated Tunneling: Efficient routing
dynamic, public address assignment to mobile devices
23 April 2017
Ramjee

118. Power-up Internet 1.1.1.100->port 4, 239.0.0.1
>wireless, R 2 3 1 4 5
MY IP:
BS IP:
Domain
Root
Router 2
Router 1
BS1
BS2
BS3
BS4
HAWAII
Mobile IP
23 April 2017
Ramjee

119. Design Principle III:Soft-state
Host-based routing entries maintained as soft-state
Base-stations and mobile hosts periodically refresh the soft-state
HAWAII leverages routing protocol failure detection and recovery mechanisms to recover from failures
Recovery from link/router failures
23 April 2017
Ramjee

120. Failure Recovery Internet Domain Root Router 2 Domain Root Router 1 1
> port 4, R 2 4 2 R 3 4 3 3
>port 3, 5 R 1 2 3 4 5 R 1 2 3 4 5 1 R 4 2 3 2
BS1
BS2
BS3
BS4
>wireless, 1
MY IP:
BS IP:
HAWAII
Mobile IP
23 April 2017
Ramjee

121. Path Setup Schemes Host-based routing within the domain
Path setup schemes selectively update local routers as users move
Path setup schemes customized based on user, application, or wireless network characteristics
Micro-mobility handled locally with limited disruption to user traffic
23 April 2017
Ramjee

122. Micro-Mobility Internet 1.1.1.100->port 3 (4), 239.0.0.15
MY IP:
BS IP:
Domain
Root
Router 2
Router 1
BS1
>wireless,
BS2
BS3
BS4
>port 1(wireless),
HAWAII
Mobile IP
23 April 2017
Ramjee

123. Macro-Mobility Internet Domain Root Router 2 Domain Root Router 1
Mobile IP Home Agent:
> 1 1 R 4 2 R 2 3 4
> port 3, 3 3 5 4
>port 2, 6 5 R 1 2 3 4 5 R 1 2 3 4 5 1 R 4 2 3 2
BS1
BS2
BS3
BS4 1
>wireless, 7
HAWAII
Mobile IP
MY IP:
BS IP:
COA IP:
23 April 2017
Ramjee

124. Simulation Topology
23 April 2017
Ramjee

125. Performance: Audio and Video
23 April 2017
Ramjee

126. TORA O'Neill/Corson/Tsirtsis "make before break" hierarchical CR IR ER
core CR IR ER MH
(0,0,0,3,i)
(0,0,0,4,i)
(0,0,0,5,i)
(-2,0,0,5,i)
(-2,0,0,4,i)
(-2,0,0,3,i)
(-2,0,0,2,i)
(-2,0,0,1,i)
(-2,0,0,0,i)
(0,0,0,6,i)
(0,0,0,7,i)
(0,0,0,8,i)
(-1,0,0,5,i)
(-1,0,0,3,i)
(-2,0,0,6,i)
(-2,0,0,7,i)
(0,0,0,1,i)
(0,0,0,2,i) AR
(-1,0,0,4,i)
interior
edge
access
23 April 2017

127. Hierarchical Mobility Agents
GMA
RMA
Home Agent
LMA
Localize signaling to visited domain
Regional Registration/Regional Binding Update
uses IP tunnels (encapsulation)
only, only one level of hierarchy
23 April 2017
Perkins

128. Example: hierarchical FA (Dynamics, HUT)CN HA
Location update latencies for some transitions
HFA
FA1
FA11
FA12
FA2
FA3
FA13
FA29
FA14
FA15
FA31
FA13
FA32
Forsberg et al
23 April 2017

129. Hierarchical FA with soft hand-off
Data stream:
100kB/s, 1kB packets (100 packets/s)
OLD
NEW
Lost packets/ FA FA
update
FA11
FA31
0.00
FA31
FA29
0.00 CN HA
FA29
FA32
0.00
OLD
NEW
Lost packets/
FA31
FA13
0.00 FA FA
update
FA12
FA15
0.00
FA11
FA31
0.27
HFA
FA15
FA31
0.03
FA31
FA29
0.27
FA11
FA12
FA32
FA11
0.07
FA29
FA32
0.00
FA13
FA12
0.10
FA31
FA13
0.15
Data stream
CN --> MN
FA12
FA15
0.14
FA13
FA3
FA3
FA3
FA29
FA14
FA15
FA15
FA31
0.00
FA32
FA11
0.00
FA31
FA32
FA13
FA12
0.00
HUT Dynamics
802.11
Data stream
MN --> CN
23 April 2017

130. Castelluccia/Bellier
INRIA HMIPv6
inter-site (global, macro) vs. intra-site (local, micro)
CH only aware of inter-site mobility
MIPv6 used to manage macro and micro mobility
define MN as LAN connected to border router, with >= 1 MS
use site-local IPv6 addresses?
Internet MN MS BR
Site1
Castelluccia/Bellier
23 April 2017

131. INRIA HMIPv6 MH gets 2 CoA: Internet MH registers
VCoA in the MN  stays constant within site
PCoA (private CoA)  changes with each micromove
MH registers
 external CH
 local CHs
(VCoA, PCoA)  MS
MH obtains MS address and MN prefix via router advertisements
Internet
(VCoA,PCoA)
PCoA
VCoA
23 April 2017

132. INRIA HMIPv6 – packet delivery
External CH sends to VCoA
MS in MN intercepts and routes to MH
Local CH sends to PCoA
Internet MN MS
Site1
23 April 2017

133. INRIA HMIPv6 – micro mobility registration
MH moves and gets new PCoA (PCoA1)
sends BU (VCoA, PCoA1) to its MS
sends BU PCoA1) to local CHs
Internet
(VCoA,PCoA) MS
(HA,PCoA)
PCoA1
23 April 2017

134. Other approaches to latency reduction
IP-based soft handoff
buffering of in-flight data in old FA
forward to new CoA or new BS
multicast to multiple base stations
unicast  multicast  unicast
often, down some hierarchy
multicast address assignment?
UMTS / "vertical" hand-off
UMTS as "background radiation"
Domain1
Domain2 MA 1 2 3 4
Hartenstein et al.
23 April 2017

135. Comparison of CIP, HAWAII, HMIP
Cellular IP
HAWAII
HMIP
OSI layer L3
"L3.5"
Nodes
all CIP nodes
all routers
FAs
Mobile host ID
home address
care-of-address
Intermediate nodes
L2 switches
L3 routers
Means of update
data packet
signaling msg.
Paging
implicit
explicit
Tunneling no
yes
L2 triggered hand-off
optional
MIP messaging
Campbell/Gomez-Castellanos
23 April 2017

136. Network-assisted hand-off
Network makes hand-off decision, rather than UE
network sets up resources (QoS) to new FA/BS
simultaneous bindings kept and destroyed by network
allows seamless handoff
IP nodes may need to report PHY measurements (like GSM)
e.g., Hartenstein et al., Calhoun/Kempf (FA-assisted hand-off)
may need to be able to predict next access point
23 April 2017

137. Cost of networking Modality
mode
speed
$/MB (= 1 minute of 64 kb/s videoconferencing or 1/3 MP3)
OC-3 P
155 Mb/s
$0.0013
Australian DSL
(512/128 kb/s)
512/128 kb/s
$0.018
GSM voice C
8 kb/s
$0.66-$1.70
HSCSD
20 kb/s
$2.06
GPRS
25 kb/s
$4-$10
Iridium
10 kb/s
$20
SMS (160 chars/message) ?
$62.50
Motient (BlackBerry)
$133
23 April 2017

138. Generally, license limited to 10-15 years
Spectrum cost for 3G
Location
what
cost UK 3G
$590/person
Germany
$558/person
Italy
$200/person
New York
Verizon
(20MHz)
$220/customer
Generally, license limited to years
23 April 2017

139. Multimodal networking
= use multiple types of networks, with transparent movement of information
technical integration (IP)  access/business integration (roaming)
variables: ubiquity, access speed, cost/bit, …
2G/3G: rely on value of ubiquity immediacy
but: demise of Iridium and other satellite efforts
similar to early wired Internet or some international locations
e.g., Australia
23 April 2017

140. Multimodal networking
expand reach by leveraging mobility
locality of data references
mobile Internet not for general research
Zipf distribution for multimedia content
short movies, MP3s, news, …
newspapers
local information (maps, schedules, traffic radio, weather, tourist information)
23 April 2017

141. Multimedia data access modalities
delay
high
low
7DS
802.11
hotspots
satellite
SMS?
voice (2G, 2.5G)
bandwidth
(peak)
23 April 2017

142. A family of access points
hotspot + cache
WLAN
2G/3G
access sharing
Infostation
7DS
23 April 2017

143. 7DS options Many degrees of cooperation server to client peer-to-peer
only server shares data
no cooperation among clients
fixed and mobile information servers
peer-to-peer
data sharing and query forwarding among peers
23 April 2017

144. communication enabled
7DS options
Query Forwarding FW
query
query
Host C
Host A
Host B
time
Power conservation on
off
time
communication enabled
Querying
active (periodic)
passive
23 April 2017

145. Dataholders (%) after 25 min
high transmission power
P2P
Mobile Info Server
Fixed Info Server 2
23 April 2017

146. Message relaying with 7DS
WAN
Host A
WLAN
messages
Gateway
WLAN
Message
relaying
Host B
Host A
23 April 2017

147. Conclusion and outlook
First packet-based wireless multimedia networks going into production
encumbered by legacy technology and business model ("minutes")
what is 4G?
store-and-forward beats interactive
SMS, vs. phone calls
cost and complexity remain the major challenges
interworking across generations, from 1876
role of multimedia in ad-hoc networks?
ad hoc access (small hop count) + backbone
23 April 2017

148. Credits Figures and results (with permission) from Ramachandran Ramjee
Emmanuel Coelho Alves
Andrew Campbell
Ashutosh Dutta
Mustafa Ergen
Javier Gomez
Wolfgang Granzow
Teemu Jalava
Wenyu Jiang
Andreas Koepsel
Maria Papadopouli
Charles Perkins
Zizhi Qiao
Ramachandran Ramjee
Henning Sanneck
Adam Wolisz
Moshe Zukerman
Kanter, Maguire, Escudero-Pascual
and others
23 April 2017

149. UMTS IP multimedia
23 April 2017