Broadband Access Networks and Services Chapter 7 IEEE Standard Byeong Gi Lee Seoul National University EE Spring 2004

BGL2 IEEE Standard Overview Operation Modes Resource Allocation Mechanism Physical Layer Comparison to IEEE

BGL3 Overview Air Interface for Fixed Broadband Wireless Access -- The “Last Mile” Broad Bandwidth –10~66 GHz : with line-of-sight –2~11 GHz : with non-line-of-sight QoS Support –Multiple service classes TDM/TDMA/OFDMA

BGL4 Overview Air Interface Nomenclature –WirelessMAN-SC : Single carrier at 10~66 GHz –WirelessMAN-SCa : Single carrier at 2~11 GHz –WirelessMAN-OFDM : OFDM at 2~11 GHz –WirelessMAN-OFDMA : OFDMA at 2~11 GHz –WirelessHUMAN : 2~11 GHz license-exempt bands Point-to-Multipoint Topology, with Mesh Extensions

BGL History Sponsors –IEEE Computer Society –IEEE Microwave Theory and Techniques Society Project Development : Summer 1998 WiMAX Forum –16 network companies : Alvarion, Fujitsu, Intel, Nokia, … –Supports IEEE Standard

BGL History Standard – (2001): Air interface of MAC and 10~66 GHz PHY –802.16a (2003): Amendment, 2~11 GHz –802.16c (2002): Detailed system profiles for 10~66 GHz –802.16d (under revision): Consolidation of , a, and c –802.16e (under revision): Apply low mobility in licensed bands

BGL7 Frequency Bands 10~66 GHz –Severe attenuation –Line-of-sight (LOS) is required –Multipath is negligible 2~11 GHz –LOS is not required –Multipath is significant –Additional functionality is required (power management, interference mitigation, ARQ, …)

BGL8 Air Interface Nomenclature

BGL9 Protocol Layering

BGL10 Protocol Layering Service Specific CS –Classification of higher layer PDUs –Payload header suppression –ATM CS and packet CS MAC CPS –System access, bandwidth allocation, connection management –QoS provisioning

BGL11 Protocol Layering Privacy Sublayer –Authentication, secure key exchange, encryption Physical Layer –Four different physical layer specifications –SC, SCa, OFDM, OFDMA

BGL12 Operation Mode Point-to-multipoint (PMP) Mode –A central base station (BS) and multiple subscriber stations (SS) –BS fully controls the downlink bandwidth –SSs share the uplink bandwidth on a demand basis (bandwidth request, grant, polling) –Four different scheduling service classes (UGS, rtPS, nrtPS, BE)

BGL13 Operation Mode Mesh Mode –Optional operation mode in WirelessMAN-OFDM –Traffic can be routed through SSs –Centralized scheduling Mesh BS : A system connected to backhaul services Mesh BS manages the uplink and downlink bandwidth –Distributed scheduling Each node exchanges its schedule and bandwidth request/grant

BGL14 BW Request/Grant Requests –SSs send requests when uplink bandwidth is required. –Stand-alone message and piggyback –Include required number of bytes Grants –Bandwidth allocation by BS to an individual SS –Connection-based request and SS-based grant

BGL15 Polling Unicast Polling –BS allocates bandwidth to an SS –The SS send bandwidth request using the allocated bandwidth –The SS returns stuff bytes if the SS does not need bandwidth –No individual polling for UGS connections

BGL16 Polling Multicast/Broadcast Polling –When insufficient BW is available for unicast polling –BS allocates bandwidth to a group of SSs –Members of the group sends requests in the allocated bandwidth –Each SS employs a contention resolution algorithm

BGL17 Uplink Scheduling Services Four Service Classes –Unsolicited grant service (UGS) –Real-time polling service (rtPS) –Non-real-time service (nrtPS) –Best effort (BE)

BGL18 Uplink Scheduling Service UGS –For real-time services that generate fixed size packets periodically –T1/E1, VoIP without silence suppression –BS offers fixed size grants periodically –Slip indicator : set when additional bandwidth is required (due to clock rate mismatches, …) –Poll me bit : request to be polled for a different, non- UGS connection

BGL19 Uplink Scheduling Service rtPS –For real-time services that generate variable size data periodically –MPEG video –BS offers periodic unicast polling –More request overhead but efficient data transport

BGL20 Uplink Scheduling Service nrtPS –For non real-time services that generate variable size data regularly –High bandwidth FTP –BS typically polls on the order of one second –Unicast or multicast/broadcast polling BE –All forms of polling are allowed

BGL21 Scheduling in Mesh Mode Centralized Scheduling –Mesh BS : connected to backhaul services –Each SS send request message to Mesh BS –Mesh BS manages the uplink and downlink bandwidth –No collision in schedule messaging

BGL22 Scheduling in Mesh Mode Distributed Scheduling –Each node broadcasts its transmission schedule and available bandwidth –Request/grant is exchanged cooperating with neighbors –Coordinated and uncoordinated –Schedule message may collide in uncoordinated mode

BGL23 Physical Sublayer PHY Characteristics –MAP message : states the slots at which transmission bursts begin –Interval usage code : describes the burst profile (modulation, coding rate, …) used on the interval –Modulation : QPSK, 16-QAM, 64-QAM, 256-QAM –FEC : RS + convolutional code (mandatory), block/convolutional turbo code (optional) –FDD/TDD (TDD only in license-exempt bands)

BGL24 Physical Sublayer Downlink Frame Structure

BGL25 Physical Sublayer Uplink Frame Structure

BGL26 Physical Sublayer Uplink Frame Structure –The structure is described in UL-MAP –Contention opportunities reserved for initial ranging –Contention opportunities reserved for response to multicast and broadcast polls –Intervals defined by data grant specifically allocated to individual SSs

BGL27 Physical Sublayer Frame Structure in Mesh Mode

BGL28 Physical Sublayer OFDM based PHY –Subchannel : set of active subcarriers, unit of resource allocation

BGL29 Physical Sublayer OFDMA Frame Structure

BGL30 Comparison to IEEE