 No mobility  Security problem  High call failure rate (line disconnection)  Delay in getting new connections  Limited value added services

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 Cordless systems with enhanced functionality (DECT)have been developed that can support higher data rates and more application such use of multiple handsets with one home base station.

 Analog cellular systems (AMPS, TACS and NMT) and digital cellular systems (GSM and CDMA IS-95).

 Generation1 (analog wireless systems)  Generation 2 system(digital wireless system) :  Generation 3 systems:-

 Global system for mobile communication.  G.S.M was though first developed in Europe  In G.S.M. System, TDMA in a combination with FDMA Is used.  The usage of each radio channel is portioned into multiple (8) time slots and each user is assigned a specific frequency\time slot combination.

- Let’s take the case of G.S.M. Band frequency to 915 MHZ - Uplink Frequency to 960 MHZ - Downlink Frequency - Each Uplink band & Download band is of 25 MHZ duration. Now 25 MHZ is divided in 125 Parts. Each part is called Channels. - 1 Channel=1 ARFCN=25 MHZ 125=200KHZ - So, 1Channel=200 KHZ. - Hence each channel becomes 200 KHZ.Each person is allocated for 1 Channel. Hence in one band of frequency 125 Persons can talk at a time.

- After FDMA each channel is of 200 KHZ. Now 200 KHZ is again divided into same slots. 125 Channels=125*8=1000 time slots. But out of 125,124 channels are used for speech transmission. One channel in each frame is left for providing gap to next frame. This one channel is used as a guard to avoid overlapping between two frames. Hence from 125 channels including TDMA no. of time slots used for traffic=124*8=992.Hence 992 persons can talk from one frame. In this way it increases the capacity of traffic. -

 Each cell is hexagonal in shape. Each cell may be of different shape and size. In highly dense area, the size of cell will be small and in lesser dense area cell size will be larger. Size of cell on highways and on main roads, cell size is optimized to cover larger length along the road. This can be made possible by using highly directive antenna.

 Consist of the mobile equipment and SIM card.  MOBILE EQUIPMENT  Uniquely identified by IMEI(international mobile subscriber identity)   SIM EQUIPMENT:-  Uniquely identified by IMSI(international mobile subscriber identity)  Also contain secret key for authentication.  Can be protected against unauthorized use by a PIN(personal identity number)  Can also store SMS message for later retrieval.  IMSI & IMEI are independent personal mobility

 BTS(BASE TRANS CEIVER STATION)  BSC(BASE STATION CONTROLLER)  HLR(HOME LOCATION REGISTER)  VLR (VISITER LOCATION REGESTER)  EIR (EQUIPMENT IDENTITY REGISTER)  WHITE LIST, GREY LIST, BLACK LIST

 AUC (AUTHENTICATION CENTRE)  OMC (OPERATION AND MAINTENANCE CENTRE)  BASE MATERIAL  CUTTING  DRILLING  ELECTROLESS PLATING

 A PCB is used to mechanically support and electrically connect electronics component using conductive path –ways or tracks. Etched from copper sheets laminated into a non-conductive substrate.

 BASE MATERIAL  CUTTING  DRILLING  ELECTROLESS PLATING  PUMICING  LAMINATION  EXPOSURE

 DEVELOPMENT  ELECTROPLATING  STRIPPING  ETCHING  Sn-Pb STRIPPING (SOLDER STRIPPING)  PISM (PHOTO IMAGE SOLDER MASK)  HAL (HOT AIR LEVELLING)  SCREEN MASKING/PRINTING  ROUTING  TESTING  QUALITY CONTROL

 The raw material used for the manufacturing of the PCB is “COPPER CLAD EPOXY LAMINATE”.

 In this technology electronics component are inserted into plated through whole (PTH) in the PCB & soldering is done at bottom side.

 Introduction  Surface mount technology reduces PCB size human work and give accuracy.  ADVANTAGE OF SMT:-  PCB size reduction  DISADVANTAGE OF SMT:-  Component identification is difficult

 E10B is a digital switching system which supports only voice communication and CIT ALKATEL of France develops this system. E10B is a telephone switching system based on electronics components and technique. this switching can be use to transmit a variety of signals telephone, telegraph Data.