Wireless Networks and Protocols

Transcription

1 WNP-MPR-qos 1 Wireless Networks and Protocols MAP-Tele Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto

2 WNP-MPR-qos 2 Topics Scheduled for Today Quality of Service» Characterization and models» Case studies» Research issues

3 WNP-MPR-qos 3 Review of QoS basic concepts QoS in wireless networks» 3GPP-QoS» IEEE-wireless-QoS

4 WNP-MPR-qos 4 Quality of Service From a user s point of view» level of satisfaction experienced by the user of an application whose traffic is delivered through a network. Depends on User s subjective evaluation and expectations Terminal capabilities Performance of networks From a network point of view» ability of providing differentiated treatment to traffic flows or traffic classes» provide them with different levels of delivery guarantees bandwidth, delay, loss» network behaviour characterizable by a set of performance parameters

5 WNP-MPR-qos 5 QoS principles The provisioning of QoS requires» cooperation of various communications layers» cooperation of network elements in the end-to-end chain QoS requirements of users/applications must be mapped into values of network service attributes Attributes of a network service» may be described by a set of performance (QoS) parameters» which must be observable, measurable and controllable Networks and users must negotiate contracts, which are described by means of offered traffic and QoS parameters

6 Mobility Security Multicast Quality of Service WNP-MPR-qos 6 QoS QoS is an end-to-end problem, handled at several communication layers Application node Application control (e.g. SIP) Application node Application Application app. control IP layer IP control plane IP user plane IP Control IP App. node-backbone control plane interface Inter-domain interface IP Control IP Application app. control IP layer IP control plane IP user plane Transport Network IP Backbone Data link App. node-backbone user plane (IP) interface Physical

7 WNP-MPR-qos 7 QoS building blocks in a packet network Data plane (traffic flows/packets) Shaping, Policing Classification & Marking Queuing and Scheduling (service discipline) Congestion control and Queue management network Control plane QoS mapping Admission control QoS routing Resource reservation/allocation Management plane Resource provisioning Policy management Traffic source/ previous network element feed-back based, end-to-end (TCO, RTP+RTCP) inter-network element packet switch (router, switch)

8 WNP-MPR-qos 8 IP QoS Models 2 service models» IntServ - oriented towards the support of QoS per flow» DiffServ - oriented towards the provisioning of QoS to traffic classes Integrated Services (IntServ) model» Resource ReSerVation Protocol (RSVP)» FlowSpec» Controlled load» Guaranteed service (maximum delay) Differentiated Services (DiffServ) model» DS field» Per-Hop Behaviours (PHB)» Assured Forwarding (AF)» Expedited Forwarding (EF)» Bandwidth broker

9 WNP-MPR-qos 9 IntServ - RSVP Resource ReSerVation Protocol (RSVP)

10 WNP-MPR-qos 10 IntServ Tspec, FlowSpec The FlowSpec - information that characterizes» the traffic to submit to the network (TSpec)» the service requested from the network (RSpec) TSpec includes the following parameters» p peak rate» r mean rate» b bucket size» M maximum datagram size» m minimum policed unit RSpec is specified only for the Guaranteed service and includes» R service rate (must be > r)» S delay slack (acceptable delay in addition to the delay obtained with R

11 WNP-MPR-qos 11 IntServ QoS Services Guaranteed Service» hard guarantees provided to real-time applications Guaranteed bandwidth Bound on end-to-end delay No losses of conforming packets on the routers» Resources reserved per flow, based on a Flowspec (TSpec and RSpec) Controlled-Load Service» emulates the service provided by a moderately loaded best-effort network» only qualitative guarantees Very high percentage of transmitted packets are successfully delivered Delay of the majority of the packets will not greatly exceed the minimum delay of a packet» The sender does not specify RSpec

12 WNP-MPR-qos 12 DiffServ DSCP field DSCP CU DSCP: differentiated services codepoint CU: currently unused

13 WNP-MPR-qos 13 Diff Serv PHB, AF, EF Per-Hop Behaviours (PHB)» Packets marked with the same DSCP, receive similar treatment 3 PHBs defined» Best effort» Assured Forwarding (AF) Service provides qualitative guarantees, based on priorities Service characterized by a high probability of packet delivery may be used to implement the Olympic service (gold, silver, and bronze classes)» Expedited Forwarding (EF) aimed at building services characterized by low packet loss ratio, low latency and low jitter

14 DiffServ - Bandwidth broker WNP-MPR-qos 14

15 QoS in UMTS WNP-MPR-qos 15

16 WNP-MPR-qos 16 Quality of Service in UMTS UMTS TE MT RAN CN EDGE NODE End-to-End Service CN Gateway TE TE/MT Local Bearer Service UMTS Bearer Service External Bearer Service Radio Access Bearer Service CN Bearer Service Radio Bearer Service RAN Access Bearer Service Backbone Bearer Service Physical Radio Bearer Service Physical Bearer Service

17 QoS management functions, UMTS bearer service, user plane WNP-MPR-qos 17 TE MT RAN CN EDGE Gateway Ext. Netw. Class if. Class if. Cond. Cond. Cond. Mapper Mapper Mapper Local BS Resource Manager Resource Manager Resource Manager Resource Manager Resource Manager Resource Manager External BS RAN phys. BS RAN Access network service BB netw ork service data f low with indication of direction

18 TE MT RAN CN EDGE WNP-MPR-qos 18 Gateway Ext. Netw. Class if. Class if. Cond. Cond. Cond. Mapper Mapper Mapper Class» Classifies and marks packet» At the entry of network (downlink GGSN, uplink terminal) Cond Traffic conditioner» Enforces compliance of flow with QoS attributes» At the entry of the network and radio segment Mapper» marks packet with QoS information related to bearer service below Resource manager» Decides when to send the packet so that QoS is satisfied» Manages the resources it sees Local BS Resource Manager Resource Manager RAN phys. BS Resource Manager data f low with indication of direction Resource Manager RAN Access network service Resource Manager Resource Manager BB netw ork service Packet queues, ARQ mechanisms, modulations and codes, power, spreading codes External BS

19 WNP-MPR-qos 19 UMTS QoS Classes Traffic class Conversational class Streaming class Interactive class Background Fundamental characteristics Preserve time relation (variation) between information entities of the stream Conversational pattern (stringent and low delay) Preserve time relation (variation) between information entities of the stream Request-response pattern Preserve payload content Destination is not expecting the data within a certain time Preserve payload content Example of the application voice streaming video Web browsing Background download of s

20 WNP-MPR-qos 20 UMTS Bearer Service Attributes Examples Traffic class ('conversational', 'streaming', 'interactive', 'background') Maximum bitrate (kbit/s)» compliance enforced by token-bucket (Maximum-bitrate, Maximum-SDU-size)» used to reserve codes in WCDMA radio interface - downlink Guaranteed bitrate (kbit/s)» traffic compliance enforced by token-bucket (Guaranteed-bitrate, Maximum-SDU-size)» Delay/ reliability attributes guaranteed only for traffic up to the Guaranteed bitrate» Used for admission control and resource allocation Maximum SDU size (octets) SDU error ratio» fraction of SDUs lost or detected as erroneous Residual bit error ratio» Undetected bit error ratio in the delivered SDUs Transfer delay (ms)» 95th percentile of the statistical delay distribution

21 WNP-MPR-qos 21 Token Bucket OK OK Non-compliant TBC b L1<TBC L2<TBC L3>TBC b-l1+r* T b-l1 Time Token Bucket Counter (TBC) - number of remaining tokens at any time

22 WNP-MPR-qos 22 QoS attributes versus traffic classes Traffic class Conversational class Streaming class Interactive class Background class Maximum bit rate X X X X Delivery order X X X X Maximum SDU size X X X X SDU format information X X SDU error ratio X X X X Residual bit error ratio Delivery of erroneous SDUs X X X X X X X X Transfer delay X X Guaranteed bit rate X X Traffic handling priority Allocation/ Retention priority X X X X X Source statistics descriptor X X Signalling Indication X

23 WNP-MPR-qos 23 UMTS Bearer Service Attributes (Rel. 7!) Traffic class Conversational class Streaming class Interactive class Background class Maximum bitrate (kbps) <= (2) <= (2) <= (2) <= (2) Delivery order Yes/No Yes/No Yes/No Yes/No Maximum SDU size (octets) <=1 500 or (4) <=1 500 or (4) SDU format information (5) (5) <=1 500 or (4) <=1 500 or (4) Delivery of erroneous SDUs Yes/No/- (6) Yes/No/- (6) Yes/No/- (6) Yes/No/- (6) Residual BER 5*10-2, 10-2, 5*10-3, 10-3, 10-4, 10-5, *10-2, 10-2, 5*10-3, 10-3, 10-4, 10-5, *10-3, 10-5, 6*10-8 (7) 4*10-3, 10-5, 6*10-8 (7) SDU error ratio 10-2, 7*10-3, 10-3, 10-4, , 10-2, 7*10-3, 10-3, 10-4, , 10-4, , 10-4, 10-6 Transfer delay (ms) 100 maximum value 300 (8) maximum value Guaranteed bit rate (kbps) <= (2) <= (2) Traffic handling priority 1,2,3 (9) Allocation/Retention priority 1,2,3 1,2,3 1,2,3 1,2,3 Source statistic descriptor Speech/unknow n Speech/unknow n Signalling Indication Yes/No (9)

24 WNP-MPR-qos 24 PDP Context Activation Procedure for Iu mode MS RAN SGSN GGSN 1. Activate PDP Context Request C1 4. Create PDP Context Request 4. Create PDP Context Response 5. Radio Access Bearer Setup 6. Invoke Trace 8. Update PDP Context Request 8. Update PDP Context Response 9. Activate PDP Context Accept C2

25 Network-Requested PDP Context Activation Procedure WNP-MPR-qos 25 MS SGSN HLR GGSN 1. PDP PDU 2. Send Routeing Info for GPRS 2. Send Routeing Info for GPRS Ack 3. PDU Notification Request 3. PDU Notification Response 4. Request PDP Context Activation 5. PDP Context Activation procedure

26 WNP-MPR-qos 26 Protocol architecture of NAS supporting PS mode, Terminal Equipment side

27 Primitives and Parameters at SMREG-SAP - MS side WNP-MPR-qos 27

28 WNP-MPR-qos 28 UMTS QoS Conceptual Models UE GGSN Remote AP Remote Host Local UE IP Bearer Service GGSN SGSN Gn/Gp Scope of PDP Context Backbone IP Network Remote Access Point Remote Host IP Bearer Layer Access Bearer Layer (eg. UMTS Bearer)

29 WNP-MPR-qos 29 Local UE does not support IP QoS The UE controls the QoS mechanisms from the UE. QoS in UMTS controlled by PDP context. QoS in backbone network controlled by DS. DS marking performed by GGSN. Application Layer (eg. SIP/SDP) QoS on remote access link controlled by DS. PDP Flow DS Uplink Data The UE may control the QoS mechanisms from received information. QoS in UMTS controlled by PDP context selected by TFT. QoS in backbone network controlled by DS. DS marking performed by RUE, or remarking by RAP. QoS on remote access link controlled by DS or other means. Application Layer (eg. SIP/SDP) PDP Flow DS Downlink Data UE GGSN Remote AP Remote Host

30 WNP-MPR-qos 30 Local UE supports DiffServ (DS) The UE controls the QoS mechanisms from the UE. QoS in UMTS controlled by PDP context. UE DS marking carried transparently. QoS in backbone network controlled by DS. DS marking performed by UE (or remarking by GGSN). Application Layer (eg. SIP/SDP) QoS on remote access link controlled by DS. PDP Flow DS Uplink Data The UE may control the QoS mechanisms from received information. QoS in UMTS controlled by PDP context selected by TFT. Remote DS marking/ggsn remarking carried transparently. QoS in backbone network controlled by DS. DS marking performed by RUE, or remarking by RAP. Application Layer (eg. SIP/SDP) QoS on remote access link controlled by DS or other means. PDP Flow DS Downlink Data UE The UE performs DS edge functions. GGSN Remote AP Remote Host

31 WNP-MPR-qos 31 Local UE supports RSVP signalling and DiffServ The UE controls the QoS mechanisms from the UE. QoS in UMTS controlled by PDP context. UE DS marking and RSVP signalling carried transparently. QoS in backbone network controlled by DS. DS marking performed by UE, or by GGSN based on PDP context signalling. RSVP signalling carried transparently. Application Layer (eg. SIP/SDP) RSVP Signalling QoS on remote access link controlled by either DS or RSVP. PDP Flow DS Uplink Data The UE may control the QoS mechanisms from received information. QoS in UMTS controlled by PDP context selected by TFT. Remote DS marking/ggsn remarking and RSVP signalling carried transparently. QoS in backbone network controlled by DS. DS marking performed by RUE (or remarking by RAP). RSVP signalling carried transparently. Application Layer (eg. SIP/SDP) RSVP Signalling QoS on remote access link controlled by either DS or RSVP. DS PDP Flow Downlink Data UE The UE performs DS edge functions and RSVP GGSN Remote AP Remote Host

32 WNP-MPR-qos 32 UMTS Radio Resource Management UMTS WCDMA What are the causes of high packet delays?» Low transmission information rate R high packet service time (transmission time) long queues high waiting time delay» Packet retransmissions caused by packet loss What are the causes of packet loss?» High BER What are the causes high BER?

33 Uplink Capacity Maximum Number ( N ) of users WNP-MPR-qos 33 Ideal power control (every sinal received same power) N users transmitting at same data bitrate R bit/s C I C 1 C( N 1) N 1 N number of users C power received form each user (W) I interference from other users (W) E I b 0 C I R W W R C I W R 1 N 1 W RN E b energy received per information bit (J/bit) I 0 Interference spectral density (J/Hz) W chip rate (chip/s) R information bitrate (bit/s) E b /I o decreases BER increases, or alternatively, for a given E b /I o, (BER), N W R 1 Eb I 0 N, R N R i i 1 need to be managed admission control

34 Load Factor, Uplink (from Holma & Toskala, 3rd edition) WNP-MPR-qos 34

35 Load Factor, Uplink (from Holma & Toskala, 3rd edition) WNP-MPR-qos 35

36 WNP-MPR-qos 36 Admission Control Based on Throughput <

37 WLAN- QoS WNP-MPR-qos 37

38 WNP-MPR-qos 38 DCF - Distributed Coordination Function Listen before-talk, CSMA/CA based Station transmist when medium is free for time greater than DIFS Random backoff used when medium is busy DIFS SIFS S1 RTS DATA SIFS SIFS AP CTS ACK DIFS S2-bo S2 DATA - Packet arrival DATA - Transmission of DATA DIFS - Time interval DIFS

39 WNP-MPR-qos 39 PCF - Point Coordination Function Contention-free frame transfer Point Coordinator (PC / AP) pools stations PIFS time used to enter Contention Free Period PIFS SIFS SIFS SIFS PIFS SIFS SIFS PC Data+Poll Data+Poll Data+Poll CF-End Beacon DATA+ACK SIFS (no response) ACK Time Contention Period Contention Free Period CP

40 WNP-MPR-qos e QoS Support for WLAN Basic elements for QoS» Traffic Differentiation 4 Access Categories, 8 Traffic Classes» Concept of Transmission Opportunity (TXOP) Transmission of multiple frames New Contention-based channel access» Enhanced Distributed Channel Access (EDCA) New Contention-free channel access» HCF Controlled Channel Access (HCCA)

41 WNP-MPR-qos 41 HCF- Hybrid Coordination Function STA STA STA PC STA STA HC STA STA STA STA STA ( Enhanced Station ) BSS (Basic Service Set) DCF PCF QBSS (Basic Service Set for QoS) EDCA HCCA

42 WNP-MPR-qos 42 HCF - Hybrid Coordination Function During Contention Period» Controlled Contention STA may send traffic with different priorities STAs may also request resources» HC can send polled TXOPs during CP During Contention Free Period» HC polls STAs and gives a station the permission to access channel» Specifies time and maximum duration of each TXOP

43 WNP-MPR-qos 43 EDCA 4 Access Categories (AC)» AC_VO (Voice)» AC_VI (Video)» AC_BE (best-effort)» AC_BK (background) Contention between ACs (and STAs) An Inter-frame Space (IFS) for each AC Arbitration Inter frame Space (AIFS) Contention-Window (CW) depends on AC Mapping Priorities into AC» IEEE 802.1D and IEEE 802.1Q AC1 AC2 AC3 AC4 Virtual Collision

44 WNP-MPR-qos 44 Access Category AIFS AIFS[AC3] AIFS[AC2] AIFS[AC1] AIFS[AC0] ACK BackOff[AC3] + Frame BackOff[AC2] + Frame BackOff[AC1] + Frame BackOff[AC0] + Frame

45 WNP-MPR-qos 45 MAC Parameters Prioritized Channel Access implemented using MAC parameters per AC AC_VOice [0] AC_VIdeo [1] AC_BE [2] AC_BK [3] AIFSN CWmin CWmax AIFS [AC] = AIFSN [AC] * aslottime + SIFS If CW[AC] is less than CWmax[AC], CW[AC] shall be set to the value (CW[AC] + 1)*2 1.

46 WNP-MPR-qos 46 Transmission Opportunity (TXOP) TXOP: duration a STA has to transmit frame(s) When will a STA get a TXOP?» Winning a contention in EDCA during Contention Period» Receiving a polled TXOP from HC

47 WNP-MPR-qos 47 Transmission Opportunity (TXOP) (cont.) In TXOP, frames exchange sequences are separated by SIFS

48 WNP-MPR-qos 48 HCF Controlled Channel Access (HCCA) Procedure similar to PCF Hybrid Coordinator (HC)» Controls the iteration of CFP and CP By using beacon, CF-End frame and NAV Mechanism (similar to PCF)» Use polling scheme to assign TXOP to STA Issue CF-poll frame to poll STA Polling can be issued in both CFP & CP

49 WNP-MPR-qos 49 Resources Managed in WLAN Resources are the time slots» Used to transmit bits according to the modulations/codes used WLAN enables to send differentiated traffic» By giving priority to realtime type traffic WLAN enables a flow to get a bit rate /delay» By using polling What needs to be managed by the HC?» The time slots available» Who uses them and when