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Outline. Wireless introduction Wireless cellular (GSM, CDMA, 3G, 4G) Wireless LANs, MAC layer Wireless Ad hoc networks routing: proactive routing, on-demand routing, scalable routing, geo-routing multicast TCP QoS, adaptive voice/video apps Sensor networks.

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Outline

Outline

Wireless introduction

Wireless cellular (GSM, CDMA, 3G, 4G)

Wireless LANs, MAC layer

Wireless Ad hoc networks

routing: proactive routing, on-demand routing, scalable routing, geo-routing

multicast

TCP

QoS, adaptive voice/video apps

Sensor networks


Outline

Access techniques for mobile communications

FDMA (TACS)

P

F

TDMA (GSM, DECT)

ATDMA (UMTS)

T

P

F

CDMA (UMTS)

T

P

F

P - Power

T - Time

F - Frequency

T


Cdma code division multiple access

CDMA (Code Division Multiple Access)

  • unique “code” assigned to each user; i.e., code set partitioning

  • all users share same frequency, but each user has own “chipping” sequence (i.e., code) to encode data

  • Note: chipping rate >> data rate (eg, 64 chips per data bit)

  • encoded signal = (original data bit) X (chipping sequence)

  • decoding:inner-product of encoded signal and chipping sequence

  • allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”)


Cdma encode decode

CDMA Encode/Decode


Cdma two sender interference

CDMA: two-sender interference


Outline

.

m

inner-product

S T = = 0

1

SSi.Ti

m

i=1

.

S S = 1

C

= (1,1,1,1)

4,1

C

= (1,1)

2,1

C

= (1,1,-1,-1)

4,2

= (1,-1,1,-1)

C

4,3

= (1,-1)

C

2,2

C

= (1,-1,-1,1)

4,4

Orthogonal Variable Spreading Factor


Spread spectrum

Spread Spectrum


Cellular wireless network evolution

Cellular Wireless Network Evolution

  • First Generation: Analog voice

    • AMPS: Advance Mobile Phone Systems

    • Residential cordless phones

    • FDMA

  • Second Generation: Digital voice

    • GSM: European Digital Cellular - TDMA

    • IS-54/136: North American - TDMA

    • IS-95: CDMA (Qualcomm)

    • DECT: Digital European Cordless Telephone


Cellular evolution cont

Cellular Evolution (cont)

  • Third Generation: Packet data

    • will combine the functions of: cellular, cordless, wireless LANs, paging etc.

    • will support multimedia services (data, voice, video, image)

    • Requirements

      • 384 Kbps for full area coverage

      • 2 Mbps for local area coverage

      • variable bit rate

      • packet traffic support

      • flexibility (eg, multiple, multimedia streams on a single connection)


Cellular evolution cont1

Cellular Evolution (cont)

  • Third Generation: Packet data

    • 2.5 G

      • GPRS (for GSM)

        (General Packet Radio Service )

      • EDGE (for GSM)

        (Enhanced Data rates for Global Evolution)

      • 1xRTT (for CDMA)

    • 3G (W-digital CDMA)

      • IMT-2000/UMTS

        (International Mobile Telecommunications)

        (Universal Mobile Transport Service)

      • WCDMA, CDMA 2000, TD-SCDMA, WiMAX

  • 3+G, 4G systems

    • OFDM, Software radio, Array antennas

    • WiMAX, LTE (Long Term Evolution) ?


Multiple migration paths are available

Multiple Migration Paths Are Available

  • 2.5G

  • 3G

  • 3+G

  • 4G

  • 2G

  • PDC

WCDMA

  • HSPDA

  • GSM

  • GPRS

  • OFDM

  • EDGE

  • Software radio

  • TDMA

  • (IS-136)

  • Array antennas

  • CDMA2000

  • CDMA (IS-95A/B)

  • CDMA One

  • 1xRTT

  • 1XEVDO/HDR

  • 1 xtreme

  • WiMAX

  • TD-SCDMA

  • WiMAX

  • LTE


Architecture

Architecture

  • System architecture

    • networking

    • addressing

  • Physical (PHY) layer

    • radio band

    • modulation

    • error control (FEC/interleaving)

    • frame structure

    • multiple access (multi-user, up/down)

  • MAC/DLC layer

    • channel mapping (control/traffic)

    • medium access techniques

    • call setup

    • standby behavior


Cellular concept

BS

BS

BS

Backbone Network

BS

BS

BS

Cellular Concept

  • Geographical separation

  • Capacity (frequency) reuse

  • Backbone connectivity


1g amps advanced mobile phone system fdma

B

B

B

C

C

C

G

G

G

A

A

A

D

D

D

F

F

F

E

E

E

1G: AMPS (Advanced Mobile Phone System) ---- FDMA

  • Frequencies are not reused in a group of 7 adjacent cells

  • To add more users, smaller cells can be used

  • In each cell, 57 channels each for A-side carrier and B-side carrier respectively

Channels are divided into 4 categories:

1. Control (base to mobile) to manage the system

2. Paging (base to mobile) to alert mobile users to incoming calls

3. Access (bidirectional) for call set up and channel assignment

4. Data (bidirectional) for voice, FAX, or data


Handoff

Handoff

  • Handoff: Transfer of a mobile from one cell to another

  • Each base station constantly monitors the received power from each mobile

  • When power drops below given threshold, base station asks neighbor station (with stronger received power) to pick up the mobile, on a new channel

  • The handoff process takes about 300 ms


Organization of cellular networks

HLR (home location

register)

– information

MSC (mobile

switching center)

VLR (visitor

location register)

– information

BS (base station)

- modulation, antenna

Organization of Cellular Networks


To register and make a phone call

To register and make a phone call

  • When phone is switched on , it scans a preprogrammed list of 21 control channels, to find the most powerful signal

  • It transmits its ID number on it to the MSC which

    • informs the local HLR

    • adds it to VLR and informs the home MSC which informs the HLR

    • registration is done every 15 min

  • To make a call, user transmits dest Ph # on random access channel; MSC will assign a data channel

  • At the same time MSC pages the destination cell for the other party (idle phone listens on all page ch.)


How does a call get to the mobile

How does a call get to the mobile ?

  • Suppose (310) 643 - 1111 is roaming in the (408) area code

  • Cell phone registers with the (408) MSC, which adds it to (408) VLR and informs the (310) HLR of the location of the cell phone

  • A call comes in for (310) 643 – 1111. Then (310) MSC queries its HLR, and directs the call to the (408) MSC

  • The (408) MSC forwards the call to the mobile


Outline

(Freq Division

Duplex)


2g digital cellular is 54 tdma system

2G: Digital Cellular: IS-54 TDMA System

  • Second generation: digital voice

  • FDMA / TDMA

  • Same frequency as AMPS – 416 ch

  • Each 30 kHz RF channel is used at 48.6 kbps

    • 6 TDM slots/RF band (2 slots per user)

    • 8 kbps voice coding

    • 16.2 kbps TDM digital channel (3 channels fit in 30kHz)

  • 4 cell frequency reuse (not 7)

  • Capacity increase per cell per carrier

    • 3 x 416 / 4 = 312 (instead of 57 in AMPS)

    • Additional factor of two with speech activity detection.


Is 54 slot and frame structure

Frame

1944 bits in 40 ms( 48600 b/s)

SLOT 1

SLOT 2

SLOT 3

SLOT 4

SLOT 5

SLOT 6

DATA1122

DATA1122

DVCC 12

SYNC228

SACCH112

R6

G6

DATA116

MOBILE TO BASE

G:GUARD TIME R:RAMP TIME

DVCC: DIGITAL VERIFFICATION COLOR CODE

RSVD: RESERVE FOR FUTURE USE

RSVD 12

DATA1130

DATA1130

DVCC 12

SYNC228

SACCH 12

IS-54 slot and frame structure

BASE TO MOBILE


2g european gsm group special mobile

2G: European GSM (Group Special Mobile)

  • Second Generation: Digital voice

  • FDMA / TDMA

  • Frequency Division duplex (890-915 MHz Up; 935-960 MHz Down)

    • 125 frequency carriers, Carrier spacing: 200 Khz

  • 8 channels per carrier (Narrowband Time Division)

  • Physical ch 124x8 = 992, reuse factor N = 3 or 4

    • Capacity per cell per carrier: 992/ N = 330 or 248

  • Speech coder: linear predictive coding (13 Kbps)

  • Modulation: Frequency Shift Keying (Gaussian Minimum Shift Keying)

  • Multilevel, time division frame structure

  • Slow frequency hoppingto overcome multipath fading


Cdma code division multiple access is 95 qualcomm san diego

CDMA (Code Division Multiple Access): IS-95 QUALCOMM, San Diego

  • Based on DS spread spectrum

  • Two frequency bands (1.23 Mhz), one for forward channel (cell-site to subscriber) and one for reverse channel (sub to cell-site)

  • CDMA allows reuse of same spectrum over all cells. Net capacity improvement:

    • 4 to 6 over digital TDMA (eg. GSM)

    • 20 over analog FM/FDMA (AMPS)


Cdma cont d

CDMA (cont’d)

  • One of 64 PS (Pseudo Random) codes assigned to subscriber at call set up time

  • RAKE receiver (to overcome multi path-fading)

  • Pilot tone inserted in forward link for:

    • power control

    • coherent reference

  • Speech activity detection

  • Voice compression to 8 kbps (16 kbps with FEC)

  • IS-95: 20 wideband channels, BW=1.25 MHz


Third generation services vs 2g

Third generation services-- vs 2G

2M

384K

64K

32K

16K

9.6K

2.4K

1.2K

video

conference

remote

medical

service

video

on

demand

video

catalogue

shopping

mobile

TV

electronic

newspaper

ISDN

internet

telephone

conference

voice

mail

distribution

services (voice)

mobile

radio

pager

electronic

publishing

distribution

services

(data)

telephone

FAX

bidirectional

unidirectional

multicast

point to point

multipoint


Outline

Third generation bandwidth assignment

-- high frequency 2 GHz, wideband 150 MHz

ITU

IMT-2000

IMT-2000

MSS

MSS

1885

1920

1980

2010

2025

2110

2170

2200

MHz

EUROPE

IMT-2000

DECT

MSS

IMT-2000

MSS

1880

1900

1980

2010

2025

2110

2170

2200

MHz

JAPAN

IMT-2000

PHS

MSS

IMT-2000

MSS

1885

1895

1918.1

1980

2010

2025

2110

2170

2200

MHz


Utran architecture umts terrestrial radio access net

Site Contr

Site Contr

Site Contr

Site Contr

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

UTRAN Architecture(UMTS Terrestrial Radio Access Net)

Core Network

Iu

Iu

UTRAN

RNS

Iur

RNS

RNC

RNC

Iub

Iub

Iub

Iub

B-node

B-node

B-node

B-node


W cdma wide band cdma

W-CDMA (Wide Band CDMA)

Key features

  • Improved capacity and coverage (over second generation); thus, backward compatible

    • high frequency 2 GHz, wideband 150 MHz

  • High degree of service flexibility: multiple, parallel services per connection; efficient packet access

  • Operator flexibility: asynchronous interstation operation; hierarchical cell structures (HCS); adaptive antenna arrays (enabled by uplink pilot symbols); TDD (Time Division Duplex) mode for asymmetric traffic & uncoordinated environments


Radio interface protocol architecture

Radio Interface - protocol architecture

C-plane

U-plane

L3

RRC

LAC

LAC

L2/LAC

LAC

Logical

channels

RLC

RLC

RLC

RLC

L2/MAC

MAC

Transport

channels

Physical Layer

L1


Layer 1 up link physical channels w cdma example

Layer 1 - up link physical channels(W-CDMA example)

Dedicated Physical

Data Channel

Data

0.667 ms

Dedicated Physical

Control Channel

Transport

format ind.

Transmit

power control

Pilot

Feedback

indicator

Slot#2

Slot#i

Slot#15

Slot#1

frame

Frame#i

superframe

Frame#72

Frame#1

Frame#2

10 ms


Layer 1 down link physical channels w cdma example

Layer 1 - down link physical channels(W-CDMA example)

DPCCH

DPDCH

Pilot

Data

TFI

TPC

0.667 ms

frame

Slot#1

Slot#2

Slot#i

Slot#15

superframe

Frame#72

Frame#2

Frame#i

Frame#1

10 ms


Wimax ieee 802 16a 3g 4g

WiMAX - IEEE 802.16a - 3G/4G?

  • Worldwide Interoperability for Microwave Access (WiMAX) is an industry trade organization to promote and certify compatibility and interoperability of broadband wireless access equipments that conform to the IEEE 802.16a specified wireless metropolitan area networks (WMAN)

  • IEEE 802.16a - support WMAN operating at 2-11 GHz that will provide broadband wireless connectivity to fixed, portable and nomadic devices

  • It supports WMAN to connect 802.11 hot spots to the Internet providing a wireless alternative to cable and DSL for last mile broadband access


Wman wireless metropolitan area networks

WMAN (wireless metropolitan area networks)


Wman configuration

WMAN Configuration

The core components of a WAN system are the subscriber station (SS) and the base station (BS)

A BS and one or more SSs can form a cell with a point-to-multipoint (P2MP) structure

The BS controls activity within the cell including access to the medium by SSs, allocations to achieve QoS and admission to the network

Multiple BSs can be configured to form a cellular wireless network. The radius of a cell can be 2-40 km while practical one is around 7-8 km with data rate as 70 Mbps per RF channel at a BS

A point-to-point (P2P) or mesh topology also supported by the IEEE 802.16 standard


Protocol stack

Protocol Stack


Wimax physical layer

WiMAX: Physical Layer

WiMAX can operate in both licensed and unlicensed bands

The 2.5 and 3.5 GHz licensed bands will be the most common bands for WiMAX applications

On 2.4 GHz and 5 GHz non-licensed bands, their usage could be limited due to interference, which can degrade QoS services

The minimum channel bandwidth for WiMAX usage is 1.75MHz per channel, while 10 MHz is considered as an optimum


Wimax physical layer1

WiMAX: Physical Layer

  • IEEE 802.16a standard featured with 256 OFDM physical layer specification conforms the ETSI HiperMAN standards

  • OFDM (Orthogonal Frequency Division Multiplexing) 正交频分复用技术

    • Multi-Carrier Modulation 多载波调制

    • 将信道分成若干正交子信道,将高速数据信号转换成并行的低速子数据流,调制到在每个子信道上进行传输

    • 正交信号可以通过在接收端采用相关技术来分开,可以减少子信道之间的相互干扰


Wimax physical layer2

WiMAX: Physical Layer

The transmission time is divided into frames that are divided into slots

In an FDD system, uplink (SS to BS) and downlink (BS to SS) subframes are time aligned on separate frequency channels

In a TDD system, each frame is divided into a downlink subframe and an uplink subframe

In both modes, the length of any frame can varyunder the control of the BS scheduler

In TDD mode, the length of any uplink and downlink subframe can also vary, allowing asymmetric allocation between uplink and downlink


Wimax physical layer3

WiMAX: Physical Layer

IEEE 802.16 has specified several physical layers:

physical layer for 10-66 GHz

physical layer for 2-11 GHz, which can be further divided into subgroups


Wimax mac layer features

WiMAX: MAC Layer Features

The on-air timing is based on consecutive frames that are divided into slots

The size of frames and the size of slots within the frames can be varied under the control in the BS

The 802.16 MAC provides a connection-oriented service to upper layers of the protocol stack

The QoS parameters for a connection can be varied by the SSs making requests to the BS to change them while a connection is maintained

While extensive bandwidth allocation and QoS mechanisms are specified, the details of scheduling and reservation management are left unstandardized


Wimax mac layer features1

WiMAX: MAC Layer Features

MAC protocal data units (MPDUs) are transmitted in time slots. MPDUs are the packets transferred between the MAC and the PHY layer

A privacy sublayer performs authentication of network access and connection establishment, key exchange and encryption of MPDUs

MAC service data units (MSDUs) are the packets transferred between the top of the MAC and the layer above

A convergence sublayer at the top of the MAC enables Ethernet, ATM, TDM voice and IP services to be offered over the MAC layer


Wimax mac layer features2

WiMAX: MAC Layer Features

  • The MAC is concerned much with performing the mapping from MSDUs to the MPDUs

  • Across MPDUs, MSDUs can be fragmented. Within MPDUs, MSDUs can be packed (aggregated).

  • Automatic retransmission request (ARQ) is used to request the retransmission of unfragmented MSDUs and fragments of MSDUs


Wimax mac layer features3

WiMAX: MAC Layer Features

Each connection in the uplink is mapped to a scheduling service associated with rules for BS to allocate the uplink capacity

The specification of the rules and the scheduling service for a particular uplink connection is negotiated at setup

4 scheduling services defined in the standard

Unsolicited grant service (UGS) carries traffic of periodical fixed units of data. The BS grants of the size negotiated at setup regularly and preemptively without an SS request.


Wimax mac layer features4

WiMAX: MAC Layer Features

Used with UGS, an SS can report status of its transmission queue and request more by the grant management subheader

The BS can allocate some additional capacity to the SS to allow it recover the normal queue state

The real-time polling service serves traffic with dynamic nature and offers periodic dedicated request opportunities to meet time requirements

An SS issues explicit requests and capacity is granted only as the real need. The overhead and latency is more. It is well suited for connections carrying VoIP, streaming video or audio traffic


Wimax mac layer features5

WiMAX: MAC Layer Features

The non-real-time polling service is similar to the real-time polling service. But connections send bandwidth requests by random access. The served traffic needs to tolerate longer delays and is insensitive to delay jitter suitable for Internet access with a minimum guaranteed rate;

A best effort service is defined without throughput and delay guarantees. An SS can send requests for bandwidth by random access or dedicated transmission opportunities if available.


Wimax mesh networks

WiMAX: Mesh Networks

Three types of important nodes in Mesh systems:

The SSs with direct links to a node are the neighbors of the node. A node’s neighbors are one-hop away from the node.

Neighbors of an SS form a neighborhood. `

An extended neighborhood contains all the neighbors of the neighborhood.


Wimax mesh networks1

WiMAX: Mesh Networks


Wimax mesh networks centralized scheduling

WiMAX: Mesh Networks--centralized scheduling

The centralized scheduling is more determined than that in the distributed scheduling mode

The network connections and topology are the same as in the distributed scheduling mode

The request and grant process uses the Mesh Centralized Scheduling (MSH-CSCH) message

The BS determines the flow assignments from the resource requests from the SSs

Then, the SSs determine the actual schedule from the flow assignments


Wimax mesh networks coordinated distributed scheduling

WiMAX: Mesh Networks-- coordinated distributed scheduling

In the coordinated distributed scheduling mode, all the nodes shall coordinate their transmissions in their extended two-hop neighborhood

Control portion of each frame is used to regularly transmit its proposed schedule on a PMP basis to all its neighbors

Within a given channel, all neighbors receive the same schedule

All stations in a network shall use the same channel to transmit schedule information in a format of specific resource requests and grants

Coordinated distributed scheduling ensures that transmissions are scheduled without a BS


Wimax mesh networks uncoordinated distributed scheduling

WiMAX: Mesh Networks-- Uncoordinated distributed scheduling

Uncoordinated distributed scheduling can be used for fast, ad-hoc setup of schedules on a link-by-link basis, established by directed requests and grants between two nodes

Data and control traffic are scheduled to avoid collisions

Both the coordinated and uncoordinated distributed scheduling employ a three-way handshake with MSH-DSCH message:

Request is sent to seek availabilities indicating potential slots requested and actual schedule. Grant is sent indicating a subset of the suggested availabilities that fits the request. Grant confirmation is sent back by the requester


Wimax mobility supports

WiMAX: Mobility Supports

Similar to the GSM networks, the standard of IEEE 802.16e introduces “Handover” schemes to migrate a mobile station from the air-interface of one base station to another to provide mobility

Pre-handover process has been designed

The entire Handover process consists of the following five stages:

Cell Reselection

Handover Decision and Initiation

Synchronization to Target BS downlink

Ranging

Termination with the Serving BS

And some special scenarios of Handover process has been defined


Research issues qos service

Research Issues: QoS Service

IEEE 802.16d has been designed to support multimedia service with different QoS requirements

The BS can determine the number of time slots that each SS will be allowed to transmit in an uplink subframe

IEEE 802.16d has defined:

The framework to support QoS service in the PMP topology

The signaling mechanism for information exchange between BS and SS such as the connection set-up, BW-request, and UL-MAP

The uplink scheduling for UGS service flow

IEEE 802.16 has not defined:

The uplink scheduling algorithms to implement QoS to rtPS, nrtPS, and BE service flow

The admission control and traffic policing scheme


Research issues mesh networks

Research Issues: Mesh Networks

IEEE 802.16d has been designed to support mesh networks in order to extend the coverage of one BS and serve more SSs with limited resources

The standard has defined a framework to effectively schedule the traffic among remote SSs, relay SSs, and the BS

IEEE 802.16d has defined:

The centralized and 2 distributedscheduling mechanisms for information transmission and the Internet access from remote SSs

The management messages to deliver the scheduling information

IEEE 802.16d has not defined:

The detailed scheduling algorithms to implement 3 traffic scheduling strategies

The QoS issue and the scheduling algorithms to ensure the QoS in the mesh networking


Research issues mobility supports

Research Issues: Mobility Supports

The IEEE 802.16e standard has defined the procedures to support mobility

But the standard has not defined any decision algorithm to decide when to perform a handover

The challenge of the research on mobility support is how to design quick handover decision algorithms to perform fast handover and ensure the QoS during and after the handover

Another challenge is to how to combine the mobility support with mesh networking to implement an mobile WiMax mesh network

Another issue is to establish a comprehensive mobility management system to systematically control the mobility support


Wimax

WiMAX


New physical layer

New Physical Layer

  • 正交频分复用OFDM (Orthogonal Frequency Division Multiplexing) :将信道分成许多正交子信道,并在每个子信道上进行窄带调制和传输,各个子信道的载波相互正交以减少子信道间的相互干扰。

  • 多入多出MIMO (Multiple Input Multiple Output):MIMO的主要任务是将资料经过多重切割之后,经由多重天线并行同步传送。在传送的过程中,切割过的数据经由不同的天线、不同的路径反射或穿透障碍物,到达多重天线的接收端,再由相关算法重新计算后进行重组。经由多支面向不同方向的天线进行收发,一来可以减少遇到障碍物或干扰源的骚扰;二来就算遇到障碍物或干扰源也只需要重传遗失的数据而不需要全部重传。在MIMO技术的辅助下,数据流由一条变成了多条,如果其中一条遇到障碍,另外几条仍可正常传送与接收数据,重传时也只需要重新传送遗失的那一小部分数据即可。

  • 智能天线 (Smart Antena):其实这是一个由多组独立天线组成的天线阵列,天线阵列以调整相位差的方式动态地调整波束的方向,就如同加装了一支定向天线,将波束指向接收数据的目标区,以扩大无线网络的最大覆盖范围。


New physical layer1

New Physical Layer


New physical layer2

New Physical Layer


New physical layer3

New Physical Layer


New physical layer4

New Physical Layer


New physical layer5

New Physical Layer


New physical layer6

New Physical Layer


New physical layer7

New Physical Layer


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