MAC Overview NCHU CSE WMAN - 1

Transcription

1 MAC Overview NCHU CSE WMAN - 1

2 MAC Overview Connection-oriented Supports difficult user environments High bandwidth, hundreds of users per channel For variable Continuous and Burst traffic Very efficient use of spectrum Protocol-Independent core (ATM, IP, Ethernet, ) Balances between stability of contentionless and efficiency of contention-based operation Negotiate the burst profile between sender and receiver Flexible QoS offerings CBR, rt-vbr, nrt-vbr, BE, ERT-VR(16e and 16m) Supports multiple PHYs Handover NCHU CSE WMAN - 2

3 Protocol Stack Packet convergence Sublayer (PCS) ATM Packet SSCS (security sublayer ) NCHU CSE WMAN - 3

4 Fixed + Mobile Standard NCHU CSE WMAN - 4

5 Features NCHU CSE WMAN - 5

6 Brief Functions Convergence Sublayer (CS) Mapping external network data into MAC SDU» Classifying external network SDU» Associating to MAC connection ID» Payload header suppression (PHS) Common Part Sublayer (CPS) Core MAC functionality» System access» Bandwidth allocation» Connection establishment» Connection maintenance» Handover and Power management Security Sublayer PHY» Authentication (RSA X.509/EAP)» Security key exchange (3DES)» Encryption (AES) Multiple sections NCHU CSE WMAN - 6

7 Service Specific Convergence Sublayer (SSCS) The CS performs the following functions: accepting higher-layer PDUs from the higher layer performing classification of higher-layer PDUs processing (if required) the higher-layer PDUs based on the classification delivering CS PDUs to the appropriate MAC SAP receiving CS PDUs from the peer entity Currently, two CS specifications are provided Asyncronous Transfer Mode (ATM) CS Packet CS» Such as IP, PPP, Ethernet, etc., Other CSs may be specified in the future. NCHU CSE WMAN - 7

8 Packet Convergence Sublayer (PCS) Packet convergence sublayer (PCS) The packet CS resides on top of the Common Part Sublayer (CPS) The PCS performs the following functions, utilizing the services of the MAC sublayer: a) Classification of the higher-layer protocol PDU into the appropriate connection b) Suppression of payload header information (optional) c) Delivery of the resulting CS PDU to the MAC SAP associated with the service flow for transport to the peer MAC SAP d) Receipt of the CS PDU from the peer MAC SAP e) Rebuilding of any suppressed payload header information (optional) NCHU CSE WMAN - 8

9 Packet Packet Process Procedure A classifier is a set of matching criteria applied to each packet It consists of some protocol-specific packet matching criteria (destination IP address, for example), a classifier priority, and a reference to a CID. The service flow characteristics of the connection provide the QoS for that packet Several classifiers may each refer to the same service flow. (many to one) Downlink classifiers are applied by the BS to packets and uplink classifiers are applied at the SS. A packet fails to match the set of defined classifiers. CS/SS shall discard the packet. Classifier(s) CID CID/SFID PHSI mapper SFID SFID/QoS mapper SFID/PHSI (sender) CID/PHSI (receiver) PHS ruler QoS Parameters (used in scheduler) NCHU CSE WMAN - 9

10 Object model Each object has a number of attributes the attribute names that uniquely identify it are underlined. Optional attributes are denoted with brackets. NCHU CSE WMAN - 10

11 Classifications A MAC SDU is mapped onto a particular connection for transmission between MAC peers According to protocol-specific packet matching criteria (e.g. destination IP address), classifier priority and a reference to a CID (connection ID)» creates an association with the service flow ID (SFID) 32 bits service flow ID (SFID) (32 bits) Conn. ID (CID) (16 bits) PHS CID+PHSI PHS NCHU CSE WMAN - 11

12 Classifications PHS service flow ID (SFID) Conn. ID (CID) NCHU CSE WMAN - 12

13 Classifications A MAC SDU is mapped onto a particular connection for transmission between MAC peers according to protocol-specific packet matching criteria (e.g. IP address), classifier priority and a reference to a CID. SS and BS use multiple classifiers. Each classifier contains a priority field which determines the search order for the classifier. Searching algorithm is similar to policy-based search algorithm (e.g. Firewall) Classifiers can be added by dynamic signaling. Simple Network Management Protocol (SNMP)- based operations can only view Classifiers, no add/delete NCHU CSE WMAN - 13

14 Common Part Sublayer (CPS) The MAC CPS provides the core MAC functionality of system access, bandwidth allocation, connection establishment, and connection maintenance: a) System Access b) Bandwidth Request/Allocation c) Connection Establishment/Maintenance e) Quality of Service (QoS) NCHU CSE WMAN - 14

15 Security Sublayer The security sublayer providing a) authentication, b) secure key exchange c) Encryption Two component protocols Encapsulation protocol» Cryptographic suites Privacy and Key management protocol (PKMv1/v2)» Create and exchange Traffic Encryption Key (TEK) PKM Identifier (one byte)» SS uses the identifier to match a BS response to the SS requests.» In PKMv1, only SS keeps track of the identifier. (w/o mobility)» In PKMv2, both SS and BS keep track of the identifier. (w/ mobility) NCHU CSE WMAN - 15

16 Payload Header Suppression (PHS) For some payload protocols, each payload consists of an 8-bit payload header suppression index (PHSI) followed by the actual payload. A value of zero in the PHSI indicates no payload header suppression has been applied to the PDU. Otherwise, the value in the index identifies the rules for suppression. MAC header 8-bit PHSI denotes the payload header suppression field (PHSF) NCHU CSE WMAN - 16

17 Payload Header Suppression (PHS) If PHS is enabled at MAC connection, each MAC SDU is prefixed with a PHSI, which references the Payload Header Suppression Field (PHSF). The classifier uniquely maps packets to its associated PHS Rule. The receiving entity uses the CID and the PHSI to restore the PHSF. (CID+PHSI PHSF/PHSM/PHSS) When a classifier is deleted, any associated PHS rule shall also be deleted. NCHU CSE WMAN - 17

18 PHS operation NCHU CSE WMAN - 18

19 Payload Header Suppression (PHS) Rule Payload header suppression valid (PHSV) : option to verify or not verify the payload header before suppressing it Payload header suppression mask (PHSM) option to allow select bytes not to be suppressed. Such as IP sequence numbers should not be supressed Payload header suppression size (PHSS) Payload header suppression field (PHSF) Payload header suppression index (PHSI) Service flow ID (SFID). PHS rules are indexed by the combination of (SFID, PHSI) Preconfigured header format or higher-level signaling protocols are outside the scope of specification NCHU CSE WMAN - 19

20 PHS with masking A,C,E are compressed Only sends B and E NCHU CSE WMAN - 20

21 PHS Rules The BS shall define the PHSI when the PHS Rule is created The SS or BS may define the PHSS and PHSF. To change the value of a PHSF on a service flow, a new PHS rule shall be defined It is possible to partially specify a PHS rule (in particular the size of the rule) at the time a service flow is created Values of some fields [for example: IP addresses, User Datagram Protocol (UDP) port numbers, etc.] may be unknown and would be provided in a subsequent DSC as part of the activation of the service flow using the Set PHS Rule DSC Action Dynamic Service Change NCHU CSE WMAN - 21

22 PHS Signaling PHS requires the creation of the following three objects: a) Dynamic Service Flow (DSA/DSC/DSD) Addition/Change/Deletion b) Classifier c) PHS rule (PHSI is assigned by BS) NCHU CSE WMAN - 22

23 Connection ID (CID) A unidirectional mapping between BS and SS MAC peers for the purpose of transporting a service flow s traffic Connections are identified by a connection identifier (CID) All traffic is carried on a connection, even for service flows that implement connectionless protocols CID maps to a service flow identifier (SFID), which defines the Quality of Service (QoS) parameters of the service flow associated with that connection. Security associations (SAs) also exist between keying material and CIDs. NCHU CSE WMAN - 23

24 Connection ID (CID) Connections are identified by a 16-bit CID At SS initialization, three management connections in each direction (uplink and downlink) shall be established between the SS and the BS. The basic connection is used for exchanging short, timeurgent management messages.» such as DBPC-REQ/RSP : Downlink Burst Profile Change Req/Rsp, RNG-REQ/RSP : Ranging Req/Rsp The primary management connection is used for exchanging longer, more delay tolerant MAC management messages.» Such as DSA/DSC/DSD_REQ/RSP/ACK, REG_REQ/RSP The Secondary Management Connection is used for transferring delay tolerant, standards based DHCP, TFTP, SNMP, etc., management messages. (IP-based packets) NCHU CSE WMAN - 24

25 Connection ID (CID) BS returns Basic CID and Primary CID to SS via RNG-RSP messages. BS returns Secondary CID to SS via REG-RSP messages (optional). The same CID value is assigned to both members (uplink and downlink) of each connection pair. Many higher-layer sessions may operate over the same wireless CID. NCHU CSE WMAN - 25

26 Connection ID (CID) NCHU CSE WMAN - 26

27 CIDs e NCHU CSE WMAN - 27

28 Multicast and Broadcast Connections Any available traffic CID value may be used for the service SSs do not know its is multicast/broadcast Connections (MBS only from the BS view) ARQ is not applicable to multicast connections. If a downlink multicast connection is to be encrypted, each SS participating in the connection shall have an additional security association (SA) Issue : MBS in e NCHU CSE WMAN - 28

29 Envelopes Setup by BS authorized envelope provisioned authorization model dynamic authorization model NCU MWNL WMAN Service Flow - 29

30 Service Flow Addition 3-way handshaking SS-initiated DSA DSX-RVD (DSx Received) BS-initiated DSA NCHU CSE WMAN - 30

31 Service Flow Change provisioned SS-initiated DSC BS-initiated DSC NCHU CSE WMAN - 31

32 QoS (16e-2005) Global service flows Global service class names and associated AuthorizedQoSParamSets Global service class names are employed as a baseline convention for communicating AuthorizedQoSParamSet or AdmittedQoSParamSet Different from service class name (in ) 1. may not be modified by BS 2. remain consistent among all BS 3. rules-based naming system whereby the global service class name itself contains referential QoS Parameter codes. composite name parsed in nine information fields of format ISBRLSPTR (ISTBRLSPR), elements reference extensible lookup tables. NCHU CSE WMAN - 32

33 Global service flow class name (2005) NCHU CSE WMAN - 33

34 Global service flow class name (2005) parameters Uplink/Downlink indicator Maximum sustained traffic rate» peak information rate» does not include transport, protocol, or network overhead» specifies only a bound, not a guarantee that the rate is available.» The algorithm for policing this parameter is left to vendor differentiation and is outside the scope of the standard. Traffic Indication Preference Maximum traffic burst Minimum reserved traffic rate Maximum latency SDU indicator» fixed-length or variable-length Paging Preference NCHU CSE WMAN - 34

35 Rate NCHU CSE WMAN - 35

36 Delay NCHU CSE WMAN - 36

37 MAC Protocol NCHU CSE WMAN - 37

38 MAC overview Subscriber stations share the uplink to the BS on a demand basis. Four different types of uplink scheduling mechanisms Unsolicited bandwidth grants (CBR) Polling (unicast polling)» guarantees applications receive service on a deterministic basis (delay tolerant services) Contention procedures» contention may be used to avoid individual polling of SSs that have been inactive for a long period (multicast/broadcast polling) Bandwidth stealing» a portion of the bandwidth allocated in response to a bandwidth request for a connection to send another bandwidth request rather than sending data Piggyback (via grant subheader ; w/o scheduling) NCHU CSE WMAN - 38

39 MAC overview Service flows provide a mechanism for uplink and downlink QoS management. In particular, they are integral to the bandwidth allocation process. An SS requests uplink bandwidth on a per connection basis (implicitly identifying the service flow). Bandwidth is granted by the BS to an SS as an aggregate of grants in response to per connection requests from the SS. NCHU CSE WMAN - 39

40 Scheduling services Each connection is associated with a single data service. Each data service is associated with a set of QoS parameters. Managed using the DSA and DSC message dialogs. Four services are supported in Unsolicited Grant Service (UGS), Real-time Polling Service (rtps), Non-real-time Polling Service (nrtps), and Best Effort (BE). Five services are supported in e-2005 UGS (Unsolicited Grant Service) RT-VR (Real-Time - Variable Rate Service) NRT-VR (Non-Real Time - Variable Rate service) BE (Best Efforts) ERT-VR (Extended Real-Time Variable Rate) NCHU CSE WMAN - 40

41 IEEE m Service classes Real-time constant bit-rate (e.g., VoIP without silence suppression) Extended real-time variable bit-rate (e.g., VoIP with silence suppression) Real-time variable bit-rate (e.g., MPEG video) Non-real time variable bit-rate (e.g., FTP, HTTP) Best effort (e.g., ) RT-CBR ERT-VR RT-VR NRT-VR BE Data generated interval Periodic Periodic Periodic Dynamic Dynamic Packet size Fixed Fixed/ dynamic Dynamic Dynamic Dynamic Delay sensitivity High High High Middle Low NCHU CSE WMAN - 41

42 Unsolicited Grant Service (UGS) support real-time data streams consisting of fixed-size data packets issued at periodic intervals Such as T1/E1 and Voice over IP without silence suppression mandatory QoS service flow parameters Maximum Sustained Traffic Rate Maximum Latency Tolerated Jitter Request/Transmission Policy (option) Minimum Reserved Traffic Rate parameter» If present, equals to Maximum Sustained Traffic Rate parameter. In e, UGS is able to support variable length PDUs. Maximum Sustained Traffic Rate is removed Add Unsolicited Grant Interval and SDU size (if fixed) NCHU CSE WMAN - 42

43 Unsolicited Grant Service (UGS) The BS shall provide Data Grant Burst IEs to the SS at periodic intervals based upon the Maximum Sustained Traffic Rate of the service flow. The Grant Management subheader is used to pass status information from the SS to the BS regarding the state of the UGS service flow. Slip Indicator (SI) bit : set when service flow has exceeded its transmit queue depth Poll-me (PM) bit : is used to request to be polled for a different, non-ugs connection. Request : contention-free access NCHU CSE WMAN - 43

44 Real-time Polling Service (rtps) support real-time data streams consisting of variable-sized data packets that are issued at periodic intervals Such as moving pictures experts group (MPEG) video. mandatory QoS service flow parameters Minimum Reserved Traffic Rate Maximum Sustained Traffic Rate Maximum Latency Request/Transmission Policy In e,» SS uses only unicast poll request opportunities in order to obtain uplink transmission opportunities» use unsolicited Data Grant Burst Types for uplink transmission as well» contention-free manner Add Traffic priority and Unsolicited Polling Interval NCHU CSE WMAN - 44

45 Non-real-time Polling Service (nrtps) support delay-tolerant data streams consisting of variable-sized data packets for which a minimum data rate is required such as FTP mandatory QoS service flow parameters Minimum Reserved Traffic Rate Maximum Sustained Traffic Rate Traffic Priority Request/Transmission Policy» unicast poll : BS typically polls nrtps CIDs on an interval on the order of one second or less» timely unicast request opportunities : contention access» unsolicited Data Grant Burst Types NCHU CSE WMAN - 45

46 Best Effort (BE) support data streams for which no minimum service level is required and therefore may be handled on a space-available basis. mandatory QoS service flow parameters Maximum Sustained Traffic Rate Traffic Priority Request/Transmission Policy» contention request opportunities» Piggyback» Bandwidth steal» Polling NCHU CSE WMAN - 46

47 Extended Real-Time Variable Rate (ERT-VR) service support real-time applications with variable datarates, which require guaranteed data and delay, for example VoIP with silence suppression. QoS parameters (combines UGS and RT-VR) Maximum Latency Tolerated Jitter Minimum Reserved Traffic Rate Maximum Sustained Traffic Rate Traffic Priority Request/Transmission Policy Unsolicited Grant Interval NCHU CSE WMAN - 47

48 Outbound transmission scheduling is performed by BS for downlink, SS for uplink the following items are taken into account for each active service flow: The scheduling service specified for the service flow. The values assigned to the service flow s QoS parameters. The availability of data for transmission. The capacity of the granted bandwidth NCHU CSE WMAN - 48

49 QoS Scheduler NCHU CSE WMAN - 49

50 Outbound Transmission Scheduling NCHU CSE WMAN - 50