wireless communication(personal access)

1
PACS Personal Access Communication Systems

• By,
• A.POOJA SHUKLA
• ECE B
• 190912066
• SAVEETHA UNIVERSITY

2
INTRODUCTION

• 3rd generation system
• Proposed by Bellcore in 1992
• It supports voice, data, and video images
• Coverage is within 500 meter range
• Provides wireless connectivity for LECs

3
WHY CALLED AS WACS...??

• PACs concept with LECs is called Wireless
  Access Communication System
• Use of time slot, channels, frames were
  proposed for PACs
• Changes were made in channel B.W, data rate,
  no. of. Slot per frame and QPSK were chosen

4
PACS SYSTEM ARCHITECTURE
5

• Universal wireless access system for widespread
  applications
• Used in private and public telephone system
  which operate in either licensed or unlicensed
  PCS bands
• It is served by a central office in residential
  application

6
(No Transcript)
7
(No Transcript)
8
FOUR MAIN COMPONENTS

1. Subscriber unit (SU) fixed / portable
2. Radio ports (RP)
3. Radio port control unit (RPCU)
4. Access manager (AM)

9
HOW IT WORKS..?????

• Air interface provides a connection between the
  SU and RP
• SU connects through the RPs to the RPCU

10

• RPCU is connected with its RPs by using an
  Embedded Operations Channel (EOC) provided within
  the interface
• Standard contains a fixed distribution network
  and network intelligence
• Only at 500m of the distribution network is
  designed to be wireless

11
PACS RADIO INTERFACE
12

• Designed for operation in US PCS band
• Uses a large number of channels
• Channels are.,
• 1. frequency division multiplexed
• 2. time division multiplexed
• PACS and WACS channel bandwidth is 300 khz

13
HOW DOES WACS WORKS.?

• Uses TDMA with frequency division duplexing
  (FDD)
• Uses 8 time slots provided in 2ms frame on each
  radio channel
• The reverse link time slot is offset, from its
  paired forward link time slot by exactly 1 time
  slot 62.5 us

14

• FORWARD LINK
• 1850 MHz 1910 MHz
• REVERSE LINK
• 1930 MHz 1990 MHz
• UNLICENSED US PCS
• 1920 MHz 1930 MHz

15
MODULATION

• ? / 4 DQPSK modulation
• 99 of transmitted signal power is contained in
  channel
• channel bandwidth is of 288 kHz
• 8 time slots, each contains 120 bits and are
  sent in a 2.5 ms frame
• With TDD, 2 time slots apart for each user

16
SPEECH CODING

• WACS uses 32 kbps for digital speech encoding
• Provides,
• 1. low complexity
• 2. minimum cost
• 3. radio link privacy

17
PACS CHANNELS

• Provides system broadcasting channels (SBCs)
  used in paging messages
• 32 kbps SBC provides alerting and system
  information for upto 80,000 users
• forward link to synchronize,
• 1. synchronization channel
• 2. slow channel

18
MULTIPLE ACCESS

• Technology uses FDD or TDD
• Many portable handsets and data terminals can
  be served
• The radio links can be shared
• Provides a wide range of user transmission
  rates within a common architecture

19
POWER CONTROL

• The PACS subscriber unit uses adaptive power
  control to minimize battery drain during
  transmission
• Used to reduce the co-channel interference on
  the reverse path

20
THANK YOU!!!