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Mobile Communications
WMAN, WPANManuel P. Ricardo
Faculdade de Engenharia da Universidade do Porto
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Type of Wireless Networks
♦ WPAN - Wireless Personal Area Networks» short distances among a private group of devices
♦ WLAN - Wireless Local Area Networks» areas such as an home, office or group of buildings
♦ WMAN - Wireless Metropolitan Area Networks» from several blocks of buildings to entire cities
♦ PLMN - Public Land Mobile Networks» regions and countries
♦ Broadcast » single direction, audio and video
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Technologies Comparison
• U=bit/s/Hz/km2
– PLMN 10 to 40 U (based on UMTS)
– WMAN 25 to 50 U – WLAN 100 to 500 U
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Information
♦ Current Standard» Freely available at IEEE site
http://www.ieee.org publications & standards get IEEE standards
» IEEE 802.16-2009 - IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Broadband Wireless Access Systems
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IEEE 802.16 Terms
♦ MAN – Metropolitan Area Network♦ BS – Base Station♦ SS – Subscriber Station♦ DL – Downlink, from BS to SS ♦ UL – Uplink, from SS to BS♦ FDD – Frequency Division Duplex♦ TDD – Time Division Duplex♦ TDMA – Time Division Multiple Access♦ TDM – Time Division Multiplexing♦ OFDM – Orthogonal Frequency Division Multiplexing♦ OFDMA - Orthogonal Frequency Division Multiple Access♦ QoS – Quality of Service
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Topology
Source: Understanding WiMAX and 3G for Portable/Mobile Broadband Wireless, Technical White Paper, Intel.
Base Station
Subscriber StationsMobile Station
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Adaptive Burst Profiles
♦ Burst profile: Modulation and FEC
♦ On DL» multiple SSs can associate on the same DL burst
♦ On UL» SS transmits in an given time slot with a specific burst
♦ Dynamically assigned according to link conditions» Burst by burst» Trade-off capacity vs. robustness in real time
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OFDM PHY TDD Frame Structure
DL Subframe
Frame n-1
pre.
Time
Adaptive
Frame n Frame n+1
UL subframe
FCH DLburst 1
DLburst n
ULMAP
Broadcast Conrol msgs
... UL burst 1 UL burst m
DLMAP
DCDopt.
UCDopt.
...DLburst 2
UL TDMADL TDM
pre. pre.
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OFDM PHY FDD Frame Structure
DL Subframe
Frame n-1
pre.
Time
BroadcastControl Msgs
Frame n Frame n+1
UL subframe
FCH DLburst 1
DLburst k...
DL TDMA
UL burst 1 UL burst m
DLburst 2
DLburst n
DLburst k+1 ...
DL TDM
...
UL TDMA
DLMAP
ULMAP
DCDopt.
UCDopt.
pre.pre.
UL MAP for nextMAC frame UL
burstspre. pre.
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FDD MAPs Time Relevance
frame
Broadcast
Full Duplex Capable User
Half Duplex Terminal #1
Half Duplex Terminal #2
UPLINK
DOWNLINK
DL MAP
UL MAP
DL MAP
UL MAP
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IEEE 802.16 MAC Addressing and Identifiers
♦ SS has 48-bit IEEE MAC address♦ BS has 48-bit base station ID
» Not a MAC address; 24-bit used for operator indicator
♦ 16-bit connection ID (CID)♦ 32-bit service flow ID (SFID)♦ 16-bit security association ID (SAID)
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Convergence Sub-Layer (CS)♦ ATM Convergence Sub-Layer
» Support for VP/VC connections» Support for end-to-end signaling of dynamically created connections » ATM header suppression; Full QoS support
♦ Packet Convergence Sub-Layer» Initial support for Ethernet, VLAN, IPv4, and IPv6» Payload header suppression; Full QoS support
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MAC – CPS – Data Packet Encapsulations
PHSI
MAC PDU
Ethernet Packet
Ethernet Packet
Packet PDU(e.g., Ethernet)
CS PDU(i.e., MAC SDU)
HT
FEC block 1
CRCMAC PDU Payload
OFDMsymbol
1
PHY Burst(e.g., TDMA burst)
PreambleOFDMsymbol
2
OFDMsymbol
n......
FEC FEC Block 2 FEC block m......FEC Block 3
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MAC – CPS – MAC PDU Transmission
♦ MAC PDUs are transmitted in PHY Bursts♦ The PHY burst can contain multiple FEC blocks♦ MAC PDUs may span FEC block boundaries ♦ Concatenation, Fragmentation
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MAC – CPS – MAC PDU Concatenation
MAC PDU 2
HT
FEC block 1
CRCMAC PDU Payload
OFDMsymbol
1
PHY Burst(e.g., TDMA burst)
PreambleOFDMsymbol
2
OFDMsymbol
n......
FEC FEC Block 2 FEC block m......FEC Block 3
MAC PDU 1
HT CRCMAC PDU Payload ......
MAC PDU k
HT CRCMAC PDUPayload
Multiple MAC PDUs are concatenated into the same PHY burst
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MAC – CPS – MAC PDU Fragmentation
FEC block1
OFDMsymbol
1
PHY Burst
Pre.
MAC SDU
OFDMsymbol
n1......
FEC FEC Blockm1
......
MAC SDUseg-1
HT CRCMAC PDU PayloadHT CRCMAC PDU
Payload
A MAC SDU can be fragmented into multiple segments, eachsegment is encapsulated into one MAC PDU
FEC block1
OFDMsymbol
1
PHY Burst
Pre.OFDMsymbol
n2......
FEC Blockm2
......
HT CRCMAC PDUPayload
MAC SDUseg-2
MAC SDUseg-3
FSH
FSH
FragmentationSub-Header
(8 bits)
FSH
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MAC – CPS QoS
♦ Three components of 802.16 QoS » Service flow QoS scheduling» Dynamic service establishment» Two-phase activation model (admit first, then activate)
♦ Service Flow » A unidirectional MAC-layer transport service characterized by a set of
QoS parameters (latency, jitter, throughput)» Identified by a 32-bit SFID (Service Flow ID)
♦ Three types of service flows» Provisioned: controlled by network management system » Admitted: the required resources reserved by BS, but not active» Active: the required resources committed by the BS
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MAC – CPS – Uplink Service Classes
♦ UGS: Unsolicited Grant Services♦ rtPS: Real-time Polling Services♦ nrtPS: Non-real-time Polling Services♦ BE: Best Effort
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MAC – CPS – Automatic Repeat reQuest (ARQ)
♦ A Layer-2 sliding-window based flow control mechanism♦ Per connection basis♦ Only effective to non-real-time applications♦ Uses a 11-bit sequence number field♦ Uses CRC-32 checksum of MAC PDU to check data errors♦ Maintain the same fragmentation structure for Retransmission♦ Optional
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Information
♦ Current Standard» Freely available at IEEE site
http://www.ieee.org publications & standards get IEEE standards
» IEEE 802.15.1-2005 IEEE Standard for Information technology--Telecommunications and information exchange between systems-- Local and metropolitan area networks--Specific requirements. Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks
♦ Read : Section 5 - General Description
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♦ Overview» Wireless personal area networks (WPANs) are used to convey information
over short distances among a private, intimate group of participant devices. Unlike a wireless local area network (WLAN), a connection made through a WPAN involves little or no infrastructure or direct connectivity to the world outside the link. This allows small, power-efficient, inexpensive solutions to be implemented for a wide range of devices.
♦ Scope» This standard defines physical layer (PHY) and medium access control
(MAC) specifications for wireless connectivity with fixed, portable, and moving devices within or entering a personal operating space (POS). A POS is the space about a person or object that typically extends up to 10 m in all directions and envelops the person whether stationary or in motion. This standard is based upon technology originally developed by the Bluetooth Special Interest Group (SIG).
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Information
♦ Current Standard» Freely available at IEEE site
http://www.ieee.org publications & standards get IEEE standards
» IEEE 802.15.4-2006 IEEE Standard for Information technology--Telecommunications and information exchange between systems--Local and metropolitan area networks-- Specific requirements Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low Rate Wireless Personal Area Networks (LR-WPANs)
♦ Read : Section 5 - General Description
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Introduction♦ Low Rate WPAN (LR-WPAN )
» simple, low-cost communication network» wireless connectivity» applications with limited power and low throughput requirements
♦ Characteristics of an LR-WPAN» Over-the-air data rates of 250 kb/s, 100kb/s, 40 kb/s, 20 kb/s» 64-bit addresses or allocated 16-bit short addresses » Carrier sense multiple access with collision avoidance (CSMA-CA)» Low power consumption» Energy Detection (ED); Link quality indication (LQI)» Radio channels
– 16 channels in the 2450 MHz band– 30 channels in the 915 MHz band – 3 channels in the 868 MHz band
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Types of Devices
♦ Two types» FFD - full-function device
– Can operate in 3 modes: PAN coordinator, coordinator, device– FFD can talk to RFDs or other FFDs
» RFD - reduced-function device – intended for applications that are extremely simple
(light switch , passive infrared sensor)– RFD can talk only to an FFD
♦ WPAN shall include at least one FFDoperating as the PAN coordinator
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Topologies, Identifiers♦ Topologies
» star topology communication between devices and PAN coordinator» peer-to-peer topology devices may communicate directly; needs PAN coordinator
enables mesh networking - 802.15.5, IP (6lowPAN), Zigbee
♦ Identifiers» Each devices has a unique 64-bit address; short 16-bit addresses may be used» Each PAN has an identifier
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Architecture
♦ Physical layer (PHY)» activation and deactivation of the radio transceiver» ED, LQI, channel selection, clear channel assessment» transmitting and receiving data» The radio operates at the following unlicensed bands
– 868–868.6 MHz (Europe)– 2400–2483.5 MHz (worldwide)
♦ MAC sublayer» beacon management» channel access» frame validation, frame acknowledged» association and disassociation» hooks for implementing application-appropriate security mechanisms
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Superframe Structure♦ Superframe format
» defined by the PAN coordinator » bounded by beacons» can have an active and an inactive portions
♦ Beacons used to » synchronize attached devices» identify the PAN» describe superframe structure
♦ Superframe may have 2 periods» Contention access period
– Devices use slotted CSMA-CA mechanism» Contention-free period (CFP)
– Guaranteed timeslots (GTS) for devices
♦ If coordinator desires no superframe it turns off beacon transmissions » Unslotted CSMA-CA is used