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

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

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

9. 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

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

17.  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.  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. 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