22-08-2012, 03:40 PM
Fundamentals of Wireless Communication & Networks
FundamentalsOfWirelessCommunicationand Networks.ppt (Size: 248 KB / Downloads: 24)
Topics to Cover
Channel Specifications
Communication Systems
Networks
Switching Technology
Communication Problems
Networking Issues
Topics to be covered
Duplexing Methods
Frequency Division Duplexing
Time Division Duplexing
Multiple Access Methods
Frequency Division Multiple Access
Time Division Multiple Access
Code Division Multiple Access
Channel Specification
The communication channel specification involves allocating the finite radio resource in two steps:
Allocating finite radio resource for bidirectional transmissions called as Duplexing Methods and
Use resource allocated for each direction to create multiple channels for that direction, called as Multiple Access Methods.
Duplexing Methods
Duplexing methods allocate finite radio resource for bidirectional (forward/uplink/Tx or reverse/downlink/Rx) transmissions. There are two main Duplexing methods.
Frequency Division Duplexing
The two directions of transmissions are created by separately allocating radio resources, in each direction.
Time Division Duplexing
The two directions of transmissions are created by alternating the transmission time
Multiple Access Methods
These methods create multiple channels in each transmission direction (i.e. Rx & Tx).
There are three main types of multiple access methods
Frequency Division Multiple Access (FDMA)
Time Division Multiple Access (TDMA)
Code Division Multiple Access (CDMA)
FDMA
Used in multiple access protocol as a channelization protocol
Individual allocation of one or more frequency bands
Access system co-ordinates access between multiple users
E.g. Analog Mobile Phone Service (AMPS)
TDMA
This method is for shared medium networks.
It allows several users to share the same frequency channel by dividing the signal into different time slots.
Multiple stations use the same transmission medium e.g. RF channel
e.g. 2G, GSM, PDC (Personal Digital Cellular)
CDMA
It’s a spread spectrum method
The transmitter encodes the signal using pseudo random sequence which is known to receiver, who decodes the received signal.
Each different random sequence corresponds to a different communication channel.
Each user transmits using the full bandwidth.
E.g. IS-95, W-CDMA
Topics to cover
Traditional Communication Systems
FM Mobile, AM Aircraft Communications, Paging Systems, Amateur Radio, PCS, GSM
Cellular Communication Systems
1G, 2G, 2.5G, 3G, 4G and LTE
Traditional Communication Systems
FM Mobile
Used for safety applications like police, forest etc.
Narrowband FM technology with 50, 150 & 450 MHz
Transmitter emits at 5-150W and Base Station at 150W.
AM Aircraft Communication
Use Very High Frequencies (VHF) in 118-136 MHz range.
25kHz channels
Ground transmitters: source of high signal powers
Paging Systems
One way communication. Base station delivers msg to destination.
Uses FSK modulation
Traditional Communication Systems
Ham Radio
Scattered through out the frequency spectrum
Transmitter use AM modulation
Large, steerable directional arrays of High Frequencies antennas
High interference power
PCS (Personal Communication System)
Work in the range 1800-1900 MHz and 1850-1990 MHz frequency band
Inexpensive, easy to install and without tedious licensing process.
Point to Point and Point to Multipoint communications
Cellular Communication Systems
First Generation (1G)
AMPS first cellular standard
Analog, FDMA based with frequency reuse technology, supports 118 calls at any given time per tower
Mainly supports voice calls
Second Generation (2G)
Mainly Digital systems
Differentiated by Multiple Access Techniques (FDMA, TDMA and CDMA)
GSM most widely deployed, FDMA/TDMA, digital cellular technology.
IS-54, TDMA based, provides three fold increase in system capacity.
IS-95, CDMA based operate in same band as AMPS,
IS-136 and IS-95 work in dual mode (analog and digital).
Cellular Communication Systems
2.5G Systems
Improvements to existing systems in terms of access speed up to 40 times previous level.
GPRS enhancement to GSM, a packet switched data delivery mechanism, supports data rates upto 144 kbps
EDGE is enhancement to GPRS, supports data rate upto 384 kbps.
cdma2000 (1x) enhancement to CDMA, smooth transition to 3G technology cdma2000 (3x).
Cellular Communication Systems
Third Generation (3G) Systems
Being developed to offer high speed data rates connectivity to mobile customers.
Defined by ITU (International Telecommunication Union) to support high speed data rates connectivity upto 144 kbps ..> 2 Mbps.
Paving the way to explosion of multimedia services on the mobile interne.
GSM operators version of 3G technology is called W-CDMA (Wide band CDMA)
UMTS (Universal Mobile Telecommunication System) is the worldwide standard for 3G technologies.
Cellular Communication Systems
The Fourth Generation (4G) systems
Sophisticated systems with even faster radio links.
Spectral efficiency and Adaptive Modulation coding.
Bandwidth efficient Multiple Access Technology
QoS for next generation multimedia support (applications like, Multimedia Messaging (MMS), Video chat, Mobile TV, High Definition TV, Digital Video Broadcasting etc)
Interoperability with existing wireless standards and All IP packet switched networks.
Cellular Communication Systems
Long Term Evolution (3GPP-LTE)
Wireless broadband technology with low latency and multi megabit throughput based on OFDM/MIMO.
Evolution to WiMAX
Enables fixed to mobile migrations of Internet applications such as VoIP, Video Streaming, mobile TV.
Shift to all IP networks
Multilayer and multi-vendor approach to security.