2
Outlines
Reference Model
Burst profiles
Convergence sublayers
MAC PDU format
MAC PDU Transmission
Fragmentation / Packing
Request/Grant Scheme
Classes of Uplink service
Power management/Handoff
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Reference Model-Wireless Networks-Lecture Slides, Slides of Wireless Networking
This course consist on introduction to wireless communication, evolution of wireless communication systems, medium access techniques, propagation models, error control techniques, cellular systems, emerging networks. This lecture inlcudes: Reference, Model, Burst, Profile, Mac, Pdu, Format, Fragmentation, Grant, Request, Power, Handoff
Typology: Slides
2011/2012
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2
Outlines
Reference Model
Burst profiles
Convergence sublayers
MAC PDU format
MAC PDU Transmission
Fragmentation / Packing
Request/Grant Scheme
Classes of Uplink service
Power management/Handoff
3
Outlines
WiMAX Basics
802.16 Evolution
Characteristics of 802.
Why not 802.11 / 802.11 vs 802.
Network Architecture
Phy Layer
Multiple Access technique ►
HARQ
MIMO
MAC Layer
QoS ► Power Management ► Handoff
5
Adaptive Burst Profiles
Burst profile ► Modulation and FEC Dynamically assigned according to link conditions ► Burst by burst, per subscriber station ► Trade-off capacity vs. robustness in real time Roughly doubled capacity for the same cell area Burst profile for downlink broadcast channel is well-known
6
ATM Convergence Sublayer
Support for:
VP (Virtual Path) switched connections ► VC (Virtual Channel) switched connections
Support for end-to-end signaling of dynamically createdconnections:
SVCs ► soft PVCs
ATM header suppression
Full QoS support
8 Upon entering the network, the SS is assigned three managementconnections in each direction. These three connections reflect thethree different QoS requirements used by different managementlevels. ► basic connection, which is used for the transfer of short, time-criticalMAC and radio link control (RLC) messages. ► The primary management connection is used to transfer longer, moredelay-tolerant messages such as those used for authentication andconnection setup. ► The secondary management connection is used for the transfer ofstandards-based management messages such as DHCP, Trivial FTP,and SNMP. In addition to these management connections, SSs are allocatedtransport connections for the contracted services. Transport connections are unidirectional to facilitate differentuplink and downlink QoS and traffic parameters;
9
Definitions
Service Data Unit (SDU)
Data units exchanged between adjacent layers
Protocol Data Unit (PDU)
Data units exchanged between peer entities
Connection and Connection ID
a unidirectional mapping between MAC peers over the airlink(uniquely identified by a CID)
Service Flow and Service Flow ID
a unidirectional flow of MAC PDUs on a connection thatprovides a particular QoS (Uniquely identified by a SFID)
11
Generic MAC Header
msb Type (6) EC (1) HT = 0 (1) Rsv (1) CI (1) EKS (2) Rsv (1) LEN msb (3) LEN Isb (8) CID msb (8) CID Isb (8) HCS (8)
12
Three types of MAC subheader may be present.
The grant management subheader• is used by an SS to convey bandwidth management needs to itsBS. ► The fragmentation sub-header• contains information that indicates the presence and orientation inthe payload of any fragments of SDUs. ► The packing sub-header• is used to indicate the packing of multiple SDUs into a single PDU.
The grant management and fragmentation sub-headersmay be inserted in MAC PDUs immediately followingthe generic header if so indicated by the Type field.
The packing sub-header may be inserted before eachMAC SDU if so indicated by the Type field.
14
MAC PDU Transmission
MAC Message SDU 1 SDU 2 MAC PDUs PDU 1 PDU 2 PDU 3 PDU 4 PDU 5 P FEC 1 FEC 2 FEC 3 Burst MAC PDUs P Preamble FEC block
15
Fragmentation
Partitioning a MAC SDU into fragments transported inmultiple MAC PDUs
Contents of the fragmentation sub-header:
2-bit Fragmentation Control (FC)• Un-fragmented
Last fragment - First fragment - Continuing fragment ► 3-bit Fragmentation Sequence Number (FSN)• Required to detect missing continuing fragments
17
Packing Fixed-Length SDUs
MAC Header LEN = n*k+j fixed length MAC SDUlength = n fixed length MAC SDUlength = n fixed length MAC SDUlength = n fixed length MAC SDUlength = n A MAC SDUs
18
Packing Variable-Length SDUs
2 Bytes Packing Sub-Header before each SDU ► Length of SDU: 11 bits ► fragmentation control (FS): 2 bits ► fragmentation sequence number (FS): 3 bits A MAC SDUs MAC Header LEN = f Type = 00001xb PSH Length = a+ variable length MAC SDUlength = a PSH Length = b+ variable length MAC SDUlength = b PSH Length = c+ variable length MAC SDUlength = c
20
Burst profiles
Each burst profile hasmandatory exit threshold andminimum entry threshold SS allowed to request a lessrobust DIUC once above theminimum entry level SS must request fall back tomore robust DIUC once atmandatory exit threshold Requests to change DIUC donewith DBPC-REQ or RNG-REQmessages Burst Profile Z Overlap Burst Profile Y Burst Profile Overlap Burst Profile C/(N+I) (dB)
21
Transition to a more robust profile
Monitor DLdata only throughDIUC k DL data at DIUC n SS C/ (N+1)Too Low for DIUC n RNG-REQ or DBPC-REQ change to DIUC k BS Continue monitoring DLdata through DIUC n Send DL data at DIUC k DL data at DIUC kRNG-RSP or DBPC-RSPDL data at DIUC k No Yes