22-03-2011, 03:28 PM
Presented By:
Panos Tzanos
Vladimeros Vladimerou
Derek Starr
[attachment=10759]
Definition
What is WLL?
- WLL is a system that connects subscribers to the local telephone station wirelessly.
Systems WLL is based on:
– Cellular
– Satellite (specific and adjunct)
– Microcellular
Other names
– Radio In The Loop (RITL)
– Fixed-Radio Access (FRA).
A general WLL setup
WLL services
Desirable:
– Wireless feature should be transparent
– Wireline Custom features
Other:
– Business related
» Hunt groups,
» Call transfers
» Conference calling
– Calling cards, coin phones
– V.29 (9600bps)
– ISDN (64kbps)
WLL should provide…
Toll-quality service
Expand from a central office to about 5 miles
Low license cost
Subscriber costs equivalent or better than copper
Ideas for U.S. market
Supplement Copper Lines
– Easier third telephone line
– Data service
Fixed Mobile Users
– Take phone wherever you want / charged on 2 levels
– “home” could mean neighborhood
– Charged regular mobile rate if you’re on the road
Cost Considerations
Situations “made” for WLL
Environments where 3rd line is degraded might be cheaper to go wireless
Where it’s impossible to lay copper (3rd world, small islands)
Business parks, industrial areas
Speedy deployment, stop gap application till wireline is in
– 90-120 days for activation
Developed vs. Developing
Developed: Wireline 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
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
Examples
UK
– 150 PTOs have licenses for wireless
– Focus on regional networks
– WLL Commercial services
» Ionica, Atlantic Telecom, Scottish Telecom
Poland
– Most exciting market in eastern Europe
– Local loop is the bottleneck
– 150,000 WLL lines since 1996 (15% of new)
– Ericsson, Motorola contracts
Connection Setup
Important Results of Fixed to Fixed Propagation in WLLs
Signal channel is not a Rayleigh fading channel:
– Power control algorithms are simpler and can be utilized more effectively
Channel Randomness is lost:
– Makes analysis difficult
Pathloss exponent is considerably smaller (Why?):
– 20dB/dec compared to 40dB/dec
– Decreases cell capacity
– Allows for larger coverage area
No handoffs necessary:
– Decreases hardware costs and system complexity
– Increases quality of service through accurate traffic predictions
Allows usage of directional antennas:
– Can greatly reduce interference and increase cell capacity
In-Cell Interference (CDMA)
I = (Nh – 1)aS » NhaS
a = voice activity factor
Nh = total # of houses
S = power received at cell site from every house
Out-of-Cell Interference
Pathloss: 20dB/dec as opposed to 40dB/dec
Þ need to take in account more tiers
Only from houses whose antennas are directed at the center cell base station
Interference from Another Cell
Blue area is region of interferers for C
It is Not a perfect pie shape
If w = (1/2)*(antenna width)
(in radians)
W = w+2sin-1((R/D)sin(w/2))
If w<<1 and R<<D:
W = w (1+(R/D))
is the “pie” arc length
Per-Tier Interference
Integration over W and all the cells at tier n yields:
In = [aNhSw/(3sqrt(3))][1/n]
for n>4
Interference is proportional to antenna width w and inversely proportional to the tier number.
Decreasing the antenna width can greatly reduce interference.
As the number of tiers approaches infinity, so does the total interference. Therefore, system capacity is a function of the total number of tiers in the system.
Capacity comparison for 5 MHz spectrum allocation
Comparison
Examples of services provided
Marconi WipLL (wireless IP local loop)
– Based on Frequency hopping CDMA
– Internet Protocol 64kbps to 2.4Mbps rates Committed Information Rate or best effort service
Lucent WSS (wireless subscriber system)
– 800 to 5000 subscribers per switch
– Uses FDMA/FDD 12 Km to 40Km coverage
GoodWin WLL
– DECT standards
– 9.6 kbps rate
– Specified conditions -5°С...+55°С, 20...75% humidity
Future of WLL / Overview
Depends on
– economic development
– existing infrastructure of a region
Offers
– market competition
– quick deployment
– relatively reliable service at low costs
Panos Tzanos
Vladimeros Vladimerou
Derek Starr
[attachment=10759]
Definition
What is WLL?
- WLL is a system that connects subscribers to the local telephone station wirelessly.
Systems WLL is based on:
– Cellular
– Satellite (specific and adjunct)
– Microcellular
Other names
– Radio In The Loop (RITL)
– Fixed-Radio Access (FRA).
A general WLL setup
WLL services
Desirable:
– Wireless feature should be transparent
– Wireline Custom features
Other:
– Business related
» Hunt groups,
» Call transfers
» Conference calling
– Calling cards, coin phones
– V.29 (9600bps)
– ISDN (64kbps)
WLL should provide…
Toll-quality service
Expand from a central office to about 5 miles
Low license cost
Subscriber costs equivalent or better than copper
Ideas for U.S. market
Supplement Copper Lines
– Easier third telephone line
– Data service
Fixed Mobile Users
– Take phone wherever you want / charged on 2 levels
– “home” could mean neighborhood
– Charged regular mobile rate if you’re on the road
Cost Considerations
Situations “made” for WLL
Environments where 3rd line is degraded might be cheaper to go wireless
Where it’s impossible to lay copper (3rd world, small islands)
Business parks, industrial areas
Speedy deployment, stop gap application till wireline is in
– 90-120 days for activation
Developed vs. Developing
Developed: Wireline 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
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
Examples
UK
– 150 PTOs have licenses for wireless
– Focus on regional networks
– WLL Commercial services
» Ionica, Atlantic Telecom, Scottish Telecom
Poland
– Most exciting market in eastern Europe
– Local loop is the bottleneck
– 150,000 WLL lines since 1996 (15% of new)
– Ericsson, Motorola contracts
Connection Setup
Important Results of Fixed to Fixed Propagation in WLLs
Signal channel is not a Rayleigh fading channel:
– Power control algorithms are simpler and can be utilized more effectively
Channel Randomness is lost:
– Makes analysis difficult
Pathloss exponent is considerably smaller (Why?):
– 20dB/dec compared to 40dB/dec
– Decreases cell capacity
– Allows for larger coverage area
No handoffs necessary:
– Decreases hardware costs and system complexity
– Increases quality of service through accurate traffic predictions
Allows usage of directional antennas:
– Can greatly reduce interference and increase cell capacity
In-Cell Interference (CDMA)
I = (Nh – 1)aS » NhaS
a = voice activity factor
Nh = total # of houses
S = power received at cell site from every house
Out-of-Cell Interference
Pathloss: 20dB/dec as opposed to 40dB/dec
Þ need to take in account more tiers
Only from houses whose antennas are directed at the center cell base station
Interference from Another Cell
Blue area is region of interferers for C
It is Not a perfect pie shape
If w = (1/2)*(antenna width)
(in radians)
W = w+2sin-1((R/D)sin(w/2))
If w<<1 and R<<D:
W = w (1+(R/D))
is the “pie” arc length
Per-Tier Interference
Integration over W and all the cells at tier n yields:
In = [aNhSw/(3sqrt(3))][1/n]
for n>4
Interference is proportional to antenna width w and inversely proportional to the tier number.
Decreasing the antenna width can greatly reduce interference.
As the number of tiers approaches infinity, so does the total interference. Therefore, system capacity is a function of the total number of tiers in the system.
Capacity comparison for 5 MHz spectrum allocation
Comparison
Examples of services provided
Marconi WipLL (wireless IP local loop)
– Based on Frequency hopping CDMA
– Internet Protocol 64kbps to 2.4Mbps rates Committed Information Rate or best effort service
Lucent WSS (wireless subscriber system)
– 800 to 5000 subscribers per switch
– Uses FDMA/FDD 12 Km to 40Km coverage
GoodWin WLL
– DECT standards
– 9.6 kbps rate
– Specified conditions -5°С...+55°С, 20...75% humidity
Future of WLL / Overview
Depends on
– economic development
– existing infrastructure of a region
Offers
– market competition
– quick deployment
– relatively reliable service at low costs