Wireless System WWW.KAASHIVINFOTECH.COM

WHAT IS WIRELESS COMMUNICATION? Transmitting/receiving voice and data using electromagnetic waves in open space. The information from sender to receiver is carried over a well defined frequency band(channel). Each channel has a fixed frequency bandwidth & capacity(bit rate). Different channels can be used to transmit information in parallel and independently. WWW.KAASHIVINFOTECH.COM

How communication takes place? satellite Received signal Transmitting signal Transmitting antenna Receiving antenna WWW.KAASHIVINFOTECH.COM

TYPICAL FREQUENCIES FM RADIO 88 MHZ TV BROADCAST 200 MHZ GSM PHONES 900 MHZ GPS 1.2 GHZ PCS PHONES 1.8 GHZ BLUETOOTH 2.4 GHZ Wi-Fi 2.4 GHZ WWW.KAASHIVINFOTECH.COM

WHY WIRELESS COMMUNICATION? Freedom from wires. No bunch of wires running from here and there. “Auto Magical” instantaneous communication without physical connection setup e.g.- Bluetooth, Wi-Fi. Global coverage Communication can reach where wiring is infeasible or costly e.g.- rural areas,buildings,battlefield,outerspace. Stay connected,flexiblity to connect multiple devices. WWW.KAASHIVINFOTECH.COM

TYPES OF WIRELESS COMMUNICATION? RADIO TRANSMISSION:- easily generated, Omni-directional , travel long distance , easily penetrates buildings. PROBLEMS:- frequency dependent , relatively low bandwidth for data communication , tightly licensed by government. MICROWAVE TRANSMISSION:- widely used for long distance communication , give high S/N ratio , relatively inexpensive. PROBLEMS:- don’t pass through buildings , whether and frequency dependent. WWW.KAASHIVINFOTECH.COM

TYPES CONTINUED…. INFRARED AND MILIMETER WAVES:- widely used for short range communication , unable to pass through solid objects , used for indoor wireless LANs , not for outdoors. LIGHT WAVE TRANSMISSION:- unguided optical signal such as laser , unidirectional , easy to install , no license required. PROBLEMS:- unable to penetrate rain or thick fog , laser beam can be easily diverted by air. WWW.KAASHIVINFOTECH.COM

CURRENT WIRELESS SYSTEMS CELLULAR SYSTEM WIRELESS LANs SATELLITE SYSTEM PAGING SYSTEM PANs(BLUETOOTH) WWW.KAASHIVINFOTECH.COM

What is cellular system? Definition Practical Wireless communication technology in which several small exchanges (called cells) equipped with low-power radio antennas (strategically located over a wide geographical area) are interconnected through a central exchange. As a receiver (cell phone) moves from one place to the next, its identity, location, and radio frequency is handed-over by one cell to another without interrupting a call. WWW.KAASHIVINFOTECH.COM

Cellular system basic concept? High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell. Same frequencies timeslots/codes are reused by spatially separated base stations. A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another. Neighboring base stations are assigned different group of channels so as to minimize the interference. WWW.KAASHIVINFOTECH.COM

Cellular system basic concept contd… By systematically spacing base stations and the channel groups may be reuse as many number of times as necessary. SUBSCRIBER UNIT Coverage area BASE STATIONS CELLS WWW.KAASHIVINFOTECH.COM MSC PSTN

Hand over ? BSC BS1 BS3 BS2 Call ended Out of BS1 coverage & connect to BS2 Connect to Bs1 & start calling Out of BS2 coverage & connect to BS3 WWW.KAASHIVINFOTECH.COM

FREQUENCY REUSE THE NEED? Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area. Each base station is allocated a group of radio channels to be used within the same geographical area of its cell. Neighboring base stations are given different channel allocation from each other. The design procedure of allocating channel groups for all of the cellular BS within a system is called frequency reuse or frequency planning. WWW.KAASHIVINFOTECH.COM

Example of frequency reuse? Co channel cells Co channel cells WWW.KAASHIVINFOTECH.COM

How to find co -channel cell? Co channels u v 60 degree D WWW.KAASHIVINFOTECH.COM

The geometry of hexagon? Axes u and v intersect at 60 degree. Unit scale is the distance between center cells. If cell radius to point of hexagon is R then 2Rcos30=1 Or R = 1/√3. to find the distance of a point P(u , v) from the origin we use x-y to u-v coordinate transformation. R² = x² + y² x=ucos30˚ y=u+vsin30˚ r=√(v²+uv+u²) WWW.KAASHIVINFOTECH.COM

Geometry contd… N = √(i²+ij+j²) where i and j are integers. Using this equation to locate co-channel cells we start from reference cell and moves i hexagon along u axis then j hexagon along the v axis. Hence the distance between co-channel cells in adjacent cluster is given by D = √(i²+ij+j²) The number of cells in a cluster N is given by N = √(i²+ij+j²) where i and j are integers. Hence the possible values of N are 1 , 3 , 4 , 7 , 12…… WWW.KAASHIVINFOTECH.COM

Co-channel location Formation of cluster for N=7 Suppose i=2 and j=1 will give co channel cell Same color showing co-channel cells. j-=1 i=2 Co channel cells WWW.KAASHIVINFOTECH.COM

What is GSM? Global system for mobile communication is a set of ETSI standards specifying the infrastructure for a digital cellular services. GSM networks are structured hierarchically it consist of one administrative region which is assigned to a MSC. Each administrative region is made up of at least one location area (LA). LA is also called the visited area. An LA consists of several cell groups. Each cell group is assigned to a base station controller (BSC) WWW.KAASHIVINFOTECH.COM

GSM system hierarchy? LA LA GSM NETWORK MSC REGION MSC REGION CELL LOCATION AREA (LA) LA BS CONTROLLER BS CONTROLLER BS CONTR-OLLER CELL CELL LA MSC REGION WWW.KAASHIVINFOTECH.COM

OPENED VIEW OF GSM ARCHITECHTURE? NSS NMS HLR VLR AUC ISDN MSC EIR PSTN BSC OTHER NETWORKS BSS WWW.KAASHIVINFOTECH.COM Mobile station

Mobile station? Consist of two main elements. 1. The mobile equipment 2. Subscriber identity module(SIM). WWW.KAASHIVINFOTECH.COM

The Base Station Subsystem? BSS = BSC + BTS SPEECH PROCESSING MODULATION/DEMODULATION TRANSCODER MINIMIZE TRANSMISSION PROBLEM AIR INTERFACE MANAGEMENT CENTRAL N/W ELEMENT OF BSS CALL ESTABLISHMENT MOBILITY MGMT STATISTICAL RAW DATA COLLECTION RADIO PATH CONTROL AIR INTERFACE SIGNALLING WWW.KAASHIVINFOTECH.COM

THE N/W SWITCHING SUBSYSTEM? NSS = MSC + HLR + VLR + AUC + EIR MANAGE COMMUNICATION B/W USERS INCLUDE DATABASE TO STORE INFORMATION OF USER CALL CONTROL MOBILITY MGMT SUBSCRIBER DATA HANDLING CHECK IDENTITY OF USER PERMANENT STORAGE OF USER INFORMATION STORE A COPY OF HLR CHECK ROAMING PROVIDE AUTHENTICATION SECURITY CHECK IMEI NUMBER OF MOBILE WWW.KAASHIVINFOTECH.COM

N/W MANAGEMENT SUBSYSTEM? 1. MONITORING MANAGE OPERATION 4. MAINTANENCE NMS WWW.KAASHIVINFOTECH.COM

GSM TECHNOLOGY ? USE TDMA + FDMA MODULATION USED = GMSK(Gaussian minimum shift keying) UPLINK FREQUENCY = 890 – 915 MHZ DOWNLINK FREQUENCY = 935 – 960 MHZ WWW.KAASHIVINFOTECH.COM

Wireless local area network(WLAN) WLAN connect local computers Range (100 m) confined region Break data into packets Channel access is shared Backbone internet provides best service Poor performance in some application like videos Low mobility WWW.KAASHIVINFOTECH.COM

Satellite system ? Global coverage Different orbit height Optimized for good transmission Expensive base stations. Voice and data transmission Telecommunication application GPS , global telephone connection TV broadcasting , military , whether broadcasting WWW.KAASHIVINFOTECH.COM

Paging system ? Pager system Broad coverage for short messages Message broadcast from all base stations Simple terminals Optimized for one way transmission Answer back hard Overtaken by cellular Pager system WWW.KAASHIVINFOTECH.COM

Wide area paging system ? Base station City 1 Paging terminal Terrestrial link Base station City 2 Paging terminal Terrestrial link Paging control center PSTN Base station City N Paging terminal Satellite link WWW.KAASHIVINFOTECH.COM

Personal area network ? Bluetooth Cable replacement RF technology Short range(10m) 2.4 GHz band TDD duplex scheme 1 Mbps data rate shared b/w 7 devices Polling based multiple access Work on frequency hopping spread spectrum technology WWW.KAASHIVINFOTECH.COM

Ad-hoc network ? Peer to peer communication No backbone infrastructure Routing can be multihop Topology is dynamic Fully connected with different link SINRs. WWW.KAASHIVINFOTECH.COM

Ad-hoc network contd…. Ad-hoc network provides a flexible network infrastructure for many emerging applications. The capacity of such networks is generally unknown. Transmission , access and routing strategies for these networks are generally ad-hoc. Cross layer design is very critical and challenging. Energy constraints impose interesting design for trade offs communication and networking. WWW.KAASHIVINFOTECH.COM

Thank U WWW.KAASHIVINFOTECH.COM