This document defines and compares wireless local loop (WLL) networks to mobile systems. WLL uses wireless links to connect subscribers to local exchanges instead of copper cables, shortening construction periods and reducing costs. It is designed to serve subscribers at home or work with high voice quality and traffic support, unlike mobile systems meant for those on the move. The efficiency of WLL depends on factors like channel payload, signaling overhead, modulation, cell radius, and interference reduction techniques. Future technologies discussed include smart antennas, turbo codes, and multi-user detection to improve WLL network capacity.

1. By:- Mustahid Ali

2. Presentational Outline
 Definition of WLL
 Two important issue
 Capacity and Efficiency
 The Future Technologies
 Wireless Standards
 Disadvantages of WLL
 Scope of WLL

3. What is WLL ?
“In telephone network, a Wireless Local Loop is a
generic term for an access system that uses a
wireless link to connect subscriber to their local
exchange in place of conventional copper cable.
Using a wireless link shortens the construction
period and also reduces installation and operating
cost.”

5. Difference between WLL and mobile system
.
Mobile system
- connect people on the move
- universal coverage
- moderate voice quality
- Traffic per subscriber is supposed to be not
very high.


6. Difference between WLL and
mobile System
Wireless in Local Loop
- Serve subscribers at homes or offices.
-Voice quality must be high.
-Long conversation facility
-High Traffic support.

7. Efficiency Consideration
Depends on use and reuse of spectrum which is
governed by the following :
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channel pay load
signaling overhead
modulation efficiency
cell-radius
choice of multiple access
interference reduction techniques

8. Channel Pay Load
 Higher bit rate pay load large frequency resources
 Voice Communication required lower bit rate voice
codec

9. Signaling Overhead
 Used in setting up, monitoring and tearing down of a
call
 Carried out between subscriber and base stations
 More sophisticated system more signaling
requirement
 It is an overhead

10. Modulation Efficiency
 Direct bearing on efficient use of spectrum
 QAM, QPSK, MSK techniques are used
 Efficient techniques are expensive

11. Cell Radius
Subscriber Density is
N – Channels Available
e – Traffic / Subscriber in Erlang
r – Radius of a cell

12. FTDMA
- Frequency signal is divided into frequency channels
- Channels are assigned to users on demand
- Used for both analog and digital signals
TDMA
- Careers used for transmission of multiple time
multiplexed channels
- provided batter reuse factor for digital signal

13. CDMA
- Each bit is uniquely coded
- Receiver use decoder to separate data
- Interference is very small
MC-TDMA
- Use dynamic channel selection
- Frame is divide into time slots

14. Sectorization
Voice Activity Detection
Frequency Hopping

15. Capacity of WLL System
Capacity = C = Number of Subscriber/ sq. km. is

16.  S – Total spectrum available
 M – Multi Access Efficiency + Modulation
Efficiency + Effect of Overhead
 R – Reuse Efficiency
 x – Payload in bps Required / Subscriber
 Te – Trunking Efficiency
 e– Erlang Traffic / Subscriber
 ns – Number of Non Overlapping Sector used per Cell
 r – radius in KM. for each Cell

17. 
Space-Time processing
- Smart Antenna Technology
- Transmit Diversity Schemes
 Turbo Codes
 Multi User Detection

18. Wireless Standards
 First Generation Standards
-Promised Wide – Scale Mobile communication
-AMPS(USA), NTT (Japan), NMT (Europe)
 Second Generation Standards
-Marked as late eighties and early nineties
-Technology used TDMA,GSM
-Wireless Standards Used AMPS,IS-95,DECT
 Third Generation Standards
-DECT Evaluation towards third Generation

19. Disadvantages
 Relatively new technology
 Network capacity needs improvement
 Has yet to be fully implemented to maximize
utilization and economy

20. Developed vs. Developing
 Developed: Wire line service
 Firmly established, cellular penetration is relatively
high
 Incumbent operator would use it to install 2nd, 3rd lines,
coverage to rural areas
 2nd or 3rd competitive operator deploy it for fast & cost
effective deployment
 Quick way to establish market presence
 cellular complement to their offerings

21. Developed vs. Developing
 Developing
Quick & easy to deploy in countries with little copper line
service, so as to accommodate people on enormous
waiting lists for basic service
Low maintenance costs
Allows more competition in provider market

22. Potential
 Without the need to have a physical link in the last
mile, WLL offers us a variety of applications that will
further enhance our capability to communicate and
transfer information

23. Potential
 Suitable for the deployment of communication
facilities in provinces where tele-density is low and
geographical terrain is unsuitable for the setting-up of
infrastructure

24. Abbreviation Used
FDMA - Frequency Division Multiple Access
TDMA – Time Division Multiple Access
CDMA – Code Division Multiple Access
MC-TDMA – Multi Career TDMA
QAM – Quadrature Amplitude Modulation
QPSK - Quadrature Phase Shift Keying
MSK – Minimum Shift Keying
AMPS – Advance Mobile Phone Service
GSM – Global Service Mobile communication
DECT – Digital European Cordless Telephone

25. THANK
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