A Study of A Study of WiMax QoS Mechanisms WiMax QoS Mechanisms Masood KHOSROSHAHY Vivien NGUYEN Masood KHOSROSHAHY Vivien NGUYEN RMOB Project RMOB Project April 2006 April 2006 Project supervisor: Project supervisor: Prof. Philippe Godlewski Prof. Philippe Godlewski
Properties of IEEE Standard Properties of IEEE Standard 802.16 802.16 • Broad bandwidth • Broad bandwidth– –Up to 134 Up to 134 Mbit/ s Mbit/ s in 28 MHz channel in 28 MHz channel (in 10- - 66 GHz air interface) 66 GHz air interface) (in 10 • Supports multiple services simultaneously with full QoS Supports multiple services simultaneously with full QoS– – • Efficiently transport IPv4, IPv6, ATM, Ethernet, etc. Efficiently transport IPv4, IPv6, ATM, Ethernet, etc. • Bandwidth on demand (frame by frame) Bandwidth on demand (frame by frame) • • MAC designed for efficient use of spectrum MAC designed for efficient use of spectrum • • Comprehensive, modern, and extensible security Comprehensive, modern, and extensible security • • Supports multiple frequency allocations from 2 Supports multiple frequency allocations from 2- - 66 GHz 66 GHz– – • OFDM and OFDMA for non- - line line- - of of- - sight applications sight applications OFDM and OFDMA for non • TDD and FDD TDD and FDD • • Link adaptation: Adaptive modulation and coding Link adaptation: Adaptive modulation and coding– – • Subscriber by subscriber, burst by burst, uplink and Subscriber by subscriber, burst by burst, uplink and downlink downlink • Point Point - - to to- - multipoint topology, with mesh extensions multipoint topology, with mesh extensions • • Support for adaptive antennas and space Support for adaptive antennas and space- - time coding time coding • • Extensions to mobility Extensions to mobility •
802.16 MAC: Overview 802.16 MAC: Overview • Point Point - - to to- - Multipoint Multipoint • • Metropolitan Area Network Metropolitan Area Network • • Connection Connection- - oriented oriented • • Supports difficult user environments Supports difficult user environments • – High bandwidth, hundreds of users per channel High bandwidth, hundreds of users per channel – – Continuous and burst traffic Continuous and burst traffic – – Very efficient use of spectrum Very efficient use of spectrum – • Protocol Protocol- - Independent core (ATM, IP, Ethernet, Independent core (ATM, IP, Ethernet, … …) ) • • Balances between stability of contention Balances between stability of contention- - less and less and • efficiency of contention- - based operation based operation efficiency of contention • Flexible QoS offerings Flexible QoS offerings– – CBR, CBR, rt rt - - VBR, VBR, nrt nrt - - VBR, BE, VBR, BE, • with granularity within classes with granularity within classes • Supports multiple 802.16 Supports multiple 802.16 PHYs PHYs •
Subscriber Station (SS) Subscriber Station (SS) initialization has several steps: initialization has several steps: - The SS scans for downlink channel and establishes The SS scans for downlink channel and establishes - synchronization with the BS. synchronization with the BS. - It obtains transmit parameters. It obtains transmit parameters. - - It performs ranging and negotiating basic It performs ranging and negotiating basic - capabilities. capabilities. - It is authorized by the BS and performs key It is authorized by the BS and performs key - exchange. exchange. - It performs the registration and IP connectivity It performs the registration and IP connectivity - establishment. establishment. - Time of day establishment and the transfer of Time of day establishment and the transfer of - operational parameters. operational parameters. - It sets up the connections. It sets up the connections. -
PHY LAYER PHY LAYER TECHNIQUES TECHNIQUES OFDM OFDM OFDMA OFDMA
OFDM OFDM � orthogonal frequency orthogonal frequency- - division division � multiplexing multiplexing � eliminates eliminates interference interference between between � channels channels � no no ISI ( ISI ( coherence coherence band band of of channel channel) ) � � higher spectral efficiency higher spectral efficiency � � high high resistance resistance to to interference interference � ( channel channel code) code) ( � adjustable adjustable rate (adaptive modulation) rate (adaptive modulation) �
OFDM Encoder OFDM Encoder
OFDMA OFDMA � multiple user access multiple user access � � OFDM needs TDD or FDD OFDM needs TDD or FDD � � inter symbol interference immunity inter symbol interference immunity � � frequency selective fading immunity frequency selective fading immunity �
Studies of of 2 2 papers papers Studies � Ian C. Wong, Ian C. Wong, Zukang Zukang Shen Shen, Brian L. Evans, , Brian L. Evans, � and Jeffrey G. Andrews , “ “ A Low Complexity A Low Complexity and Jeffrey G. Andrews , Algorithm for Proportional Resource Algorithm for Proportional Resource Allocation in OFDMA Systems” ” , 2004. , 2004. Allocation in OFDMA Systems [ WSEA- - 04] 04] [ WSEA � Mustafa Mustafa Ergen Ergen, , Sinem Sinem Coleri Coleri, and , and Pravin Pravin � Varaiya “ “ QoS Aware Adaptive Resource QoS Aware Adaptive Resource Varaiya Allocation Techniques for Fair Scheduling in Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access OFDMA Based Broadband Wireless Access Systems” ” , IEEE Trans. Broadcast, vol. 49, , IEEE Trans. Broadcast, vol. 49, Systems no. 4, Dec. 2003. no. 4, Dec. 2003. [ ECV- - 03] 03] [ ECV
1- - Study Study of of 1 � Mustafa Mustafa Ergen Ergen, , Sinem Sinem Coleri Coleri, and , and Pravin Pravin � Varaiya “ “ QoS Aware Adaptive Resource QoS Aware Adaptive Resource Varaiya Allocation Techniques for Fair Scheduling in Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access OFDMA Based Broadband Wireless Access Systems” ” , IEEE Trans. Broadcast, vol. 49, , IEEE Trans. Broadcast, vol. 49, Systems no. 4, Dec. 2003 [ ECV- - 03] 03] no. 4, Dec. 2003 [ ECV
Resource allocation [ECV Resource allocation [ECV- -03] 03] � QoS QoS fixed fixed by by the the application application � � goal : achieving a specified data goal : achieving a specified data � transmission rate and BER for BER for each each transmission rate and user in each each transmission transmission user in
-03] 03] [ECV- OFDMA System [ECV OFDMA System
Solution [ECV Solution [ECV- -03] 03] � subcarriers are distributed subcarriers are distributed � among users among users � adaptive modulation in OFDMA adaptive modulation in OFDMA � systems systems � optimal solution for optimal solution for ressouce ressouce � allocation “ “ Integer Integer allocation Programming” ” - - data rate data rate and and Programming BER vs total power power BER vs total
Control channels channels Control • channel estimation • ressouce allocation within coherence time
-03] 03] [ECV- OFDMA System [ECV OFDMA System
Solution [ECV Solution [ECV- -03] 03] � need need of of low low complexity complexity algorithms algorithms � � need need of of solutions solutions closed closed to to the the � optimal one one optimal � subcarrier subcarrier allocation ( allocation ( linear linear � programming, , hungarian hungarian algorithm algorithm ) ) programming � adaptive modulation (bit adaptive modulation (bit loading loading � algorithm ) ) algorithm � combination combination and and improvements improvements algo algo. . � ( fair fair scheduling scheduling, , greedy greedy realising realising, , ( horizontal and and vertical vertical swapping swapping) ) horizontal
2- - Study Study of of 2 � Ian C. Wong, Ian C. Wong, Zukang Zukang Shen Shen, Brian L. , Brian L. � Evans, and Jeffrey G. Andrews , “ “ A Low A Low Evans, and Jeffrey G. Andrews , Complexity Algorithm for Proportional Complexity Algorithm for Proportional Resource Allocation in OFDMA Systems” ” , , Resource Allocation in OFDMA Systems 2004 [ WSEA- - 04] 04] 2004 [ WSEA
Resource allocation [WSEA Resource allocation [WSEA- -04] 04] � assigning subcarriers to SS assigning subcarriers to SS � � assigning power assigning power � � BER and data rate BER and data rate contraints contraints �
Fixed data rate data rate and and BER BER [WSEA Fixed [WSEA- -04] 04] � fixed user data rates and BER fixed user data rates and BER � requirements requirements � goal: minimize the total transmitted goal: minimize the total transmitted � power power � problem : need of an adaptive problem : need of an adaptive � modulation system modulation system
Rate- -adaptive adaptive [WSEA Rate [WSEA- -04] 04] � maximize the total data rate maximize the total data rate � (capacity) over all users (capacity) over all users � power and BER constraints power and BER constraints � � use of use of waterfilling waterfilling � � problem : no fairness problem : no fairness � � goal: minimum user goal: minimum user’ ’s data rate s data rate �
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