FIXED WIRELESS LOCAL LOOP
CONCEPT & WLL SYSTEM
1
FIXED WIRELESS LOCAL LOOP CONCEPT
& WLL SYSTEM
Introduction to WLL
Definition
A Local Telephone System without wire line connected to fixed radio
communication system is known as Wireless Local Loop.
BTS
BTS
Fig.
What is Wireless Local Loop (WLL) ?

WLL is sometimes called fixed cellular.

WLL system can be treated as a wireline loop system without wireline
connected.

WLL is normally used for rural or unpopulated areas.

WLL can be a quick solution for developing telephone infrastructure.
Why use WLL ?

Eliminates many problems and reduce cost inherent to wireline loop
system in certain areas.

Decreases the time to deploy a network.

Mobility and flexibility.
Advantages of WLL
Advantages over wire line

Ease of installation and deployment and lower cost.

Ease of operation, administration and maintenance and lower cost.
Advantages over Mobile

Bigger coverage area

Improved signal and reduced interference (fixed to fixed link)

Higher capacity.
2
Fixed to fixed propagation

WLL propagation (fixed to fixed)
Using free space loss formulas based on 29 dB/sec.

Mobile radio propagation (fixed to mobile)
Based on 40 dB/sec.
Under a non-multipath condition
Antenna are placed at high spots of building

C/I=10 dB under a non fading fixed to fixed condition.

C/I=18 dB under a mobile radio condition.
Frequency reuse distance is reduced
Due to the directional antennas

Fixed-to-fixed link (using directional antennas on both ends).

Mobile-to-fixed link (using directional antenna on the end).
Due to the C/I

For C/I=10 dB, the frequency reuse distance D equals 2.78 times the
cell radius R.

For C/I=18 dB, the frequency reuse distance D equals 4.6 times the cell
radius R.
No handoffs occur
Characteristics of CDMA for WLL
Large capacity

Efficient use of spectrum through frequency reuse.

Variable rate with voice activity detection.
High quality service

Error detection and correction

Diversity against fading in the air

8K/13K QCELP, 8K EVRC
Security

Spread spectrum with Pseudo-random Noise code
WLL Attributes
The link range can be 62 kms (best propagation condition)

Based on free space loss

Based on his gain antenna

Based on spread spectrum waveform
3
The capacity is higher than that of mobile radio

Based on L The required C/I (or Eb/No) is smaller due to no fading
condition.
CDMA WLL : The capacity is much more

Based on : The frequency reuse K = 1. Every sector can be treated as a
cell.
WLL Markets
Two markets for WLL
Wireless Replacement

Capable of delivering toll quality speech and performance equivalent
to wireline access

Supports more than 28.8 kbps data rates for modem and fax services.

ISDN (optional)

No mobility between the network and subscriber’s network interface
device.

For markets with fully existing wireline infrastructure and so higher
services demanded.
Wireless Wireline

Capable of supporting wireline-like services

Capable of delivering performance equivalent to cellular voice quality.

Supports FAX and Modem service at lower date rates

Limited mobility support (optional) – e.g., Wirelss phone.

For markets without fully existing wireline infrastructure and so fast
expansion required.
System specification : Application to two Markets
Wireline Replacement
Wireless Wireline
Multiple access
W-CDMA
CDMA, TDMA
Channel bandwidth
3.5/5/10 MHz
1.24 MHz, 200 kHz
Voice coding
16 K LD-CELP
32 K ADPCM
8 K/13 K QCELP
65 K PCM
8 K EVRC
Data Rate
More than 28.8 Kbps
Less than 14.4 Kbps
Services
PSTN-based services available Cellular services including
including ISDN
limited mobility
Market share
Need to be field-proved
Fast adaptable on demand
4
INTRODUCTION TO STAREX-WLL
5
Subsystems
BSC (Base Station Controller)

Provides network interface to PSTN, control and management for one
or more BTSs.

Provides data internet working

System OA and M
BTS (Base Station Transceiver Subsystem)

Provides the means for a subscriber unit to access network services
using radio.

Consists of radio devices, antenna and equipment
Subscriber Unit

Used by subscribers to access network services over a radio interface.

Can provide external interfaces with terminals.
System approach
V 5.2 Type

Subscriber line signalling

Compatible with existing infrastructure

PSTN based services available

Good for operators who have wire-based network infrastructure
R2/No.7 Type

Intersystem signalling

Independent network configuration and services available

Good for new operators
Two types of BSC
BSC for R2/SS No.7 Interface

Acts as an local exchange

Supports 20K subscribers (at 0.1 Erlang/Subscriber, BP=1%) including
512 subscribers for data service.

Local accounting and switching available.
BSC for V5.2 interface

Acts as an access network

Dependent on PSTN local exchange

Supports 10K subscribers for voice (at 0.1 Erlang/subscriber, BP=1%)
including 256 subscribers for data service
6
Services




Voice
Data services
Customer calling services
Mobility
Voice



8 K QCELP
13 K QCELP
8 K EVRC
Fig.
Diagram of Data Services (Circuit)
7
Custom calling services
R2/No.7 System

Call forwarding

Call waiting

Call transfer

Caller line identification presentation/caller
restriction

3 way calling/conference call

Malicious call trace

Authentication etc.
line
identification
V 5.2 System

All feature services except data service are provided by PSTN LE but
WLL can support services transparently
Mobility
Between sectors within a BTS (default)

softer handoff
Fig.
8
Between BTSs within a BSC (Optional)

Soft handoff

Mobility between BTSs affects the system capacity

It needs to reserve channels for handoff
System features
IS-95 CDMA based system

High capacity with wide coverage

Efficient network design
Reliability and flexibility

Redundancy of major parts

Modular structure
Services

Capable of supporting wireline like services

Capable of delivering speech quality and performance equivalent to
cellular

Supports FAX and modem service at max. 14.4 Kbps data rate

Limited mobility support (optional)
BSC
BSC Function
Call Processing between WLL network and PSTN

handoff

Transcoding between 64 kbps PCM data and CDMA QCELP data and echocancelling

Subscriber Management

authentication, mobility management

Customer calling services (R2/No.7 only).

Provides interfaces to PSTN

Data inter-networking (IWF)

Provides OA&M of WLL system through BSM
9
Fig.
BSC Block Diagram (V5.2)
Fig.
BSC IPC Network (V5.2)
10
Fig.
System Block Diagram (R2/No.7)
Fig.
BSC IPC Network (R2/No.7)
11
BSC Architecture
SNIP (Switching & Network Interface Part)

Switching

PSTN interface
WAP (Wireless Access Part)

Call control

Transcoding

Interworking function
BSM (Base Station Manager)

OA&M
Fig.
Switching & Network Interface (V5.2)
12
Fig.
Switching & Network Interface (R2/No.7)
TSW





Time division switching function
Provides function of exchanging time slot for communication path.
Connects to vocoder elements and trunk interface units.
Transceives intersystem signalling, voice and data with other systems.
If R2/No.7 system as a local exchange, connects conference mixer,
voice message handling unit for local services.
ASP (R2/No.7 only)



Manages and controls call resources for interworking between air
interface and PSTN interface.
Controls signalling for PSTN interface.
Generates generic data for accounting.
OCP



S/W loading to processors.
Controls routing for intersystem call.
For R2/No.7 System
collects data for accounting and records them to the disk and
magnetic tape unit.
13


For V5.2 System
manages and controls call resources for interworking between
air interface and PSTN interface.
controls signalling for PSTN interface.
controls V5.2 protocol.
Provides function of operation, administration and maintenance.
WTFC




Provides communications path for IPC nodes as the IPC network in
SNIP (Switching & Network Interface Part).
Packet routing for control and traffic data.
Generates and distributes system clock from GPS (Global Positioning
System).
Collects alarm of H/W and environment and reports.
DCI


Provides E1/T1 PCM trunk interface
max. 64 E1 links for R2/No.7
max. 32 E1 links for V5.2.
Trunk test
Others


For R2/No.7 System
Provides R2 signalling and DTMF tone (LSI).
Provides supplementary services such as 3-way calling and
conference calling (CMX).
Provides announcement messages (VMH).
Provides No.7 signalling (CCSP).
For V5.2 System
Performs V5.2 protocol (VCP).
CCP



Manages and controls call resources.
Controls PSTN interface signalling.
Generates generic data for accounting.
14
Fig.
Wireless Access Part
CSB/IWF





Transcoding between 64K PCM data from PSTN and QCELP data.
Cancels echo because of transmission delay between in the terrestrial
and in the air.
Selects the best of channels received from BTSs in case of handoff.
Controls transmit power between BTSs and subscriber units.
Provides asynchronous data and fax services.
Provides 8 modem channels per board.
15
CIN



Provides communications path for IPC nodes in WAP (Wireless
Access Part).
IPC (Inter-Processor Communications) means communications
between processors in the system.
Packet routing for control and traffic data.
Provides interfaces to the BTS and BSM.
Max. 48 BTSs.
BSM






Provides user interface.
Operation & Maintenance.
System Configuration.
S/W downloading.
Supervision of System Status.
Provides OMC interface through TCP/IP over X.25.
BSC Configuration (V5.2)


Fig.
Accommodates 1,024 vocoder elements and 128 modem channels.
One CSB has 128 vocoder elements (or modem channels).
IWF can be mounted on CSB block.
DCI canhave 32 E1 trunks for PSTN interface.
16
BSC (V5.2) Specification
Item
Selector/Vocoding Channel Capacity
Specification
1,024 channels
 8 SVC CH/PBA
 16 PBA/shelf (128 SVC CH)
 Up to 8 shelves (SVC CH)
IWF Capacity
256 channels
 8 channels/PBA
 16 PBA/shelf (128 channels)
 up to 2 shelves
The number of BTSs supported by 1 BSC
(where one BTS is 1FA/1 sectors, 13K
vocoding, BP=1%)
Up to 48
to BTS
to PSTN
Ports
Switch network
48 E1
32 E1
T-switch (2K*1K)
Power
Requirements
Primary
Back-up
DC -48V (-43V ~ -55V)
DC –48V (-43V ~ -55V)
Environmental
Requirements
Temperature
Humidity
0~50oC
0~90%
Space Requirements
BSC (V5.2) Capacity
Item
Subscriber traffic at busy hour
Average Call Holding Time
BHCA per subscriber
Blocking Probability (GOS)
Call Processing Capacity
Traffic Handling Capacity
The Number of Subscribers Accommodated

750(W) * 650(D) * 1886(H) mm
Capacity
0.1 Erlang (originating + terminating)
90 sec.
4 BHCA/Sub.
1%
70,000 BHCA
Max. 995 Erlang
9,950 Subscribers
Performance value above is call processing capacity of half call
(originating : terminating = 50:50) in view of only voice call
processing without considering effects of authentication and mobility
(location registration, paging, softer handoff).
17
BSC Configuration (R2/No.7)


Fig.
Accommodates 1,920 vocoder elements and 256 modem channel
One CSB has 128 vocoder elements (or modem channels).
IWF can be mounted on CSB block
DCI can have 64 E1 trunk for PSTN interface.
BSC (R2/No.7) Specification
Item
Specification
Selector/Vocoding Channel Capacity
1,920 channels
 8 SVC CH/PBA
 16 PBA/shelf (128 SVC CH)
 Up to 15 shelves (SVC CH)
IWF Capacity
512 channels
 8 channels/PBA
 16 PBA/shelf (128 channels)
 up to 4 shelves
The number of BTSs supported by 1 BSC
(where one BTS is 1FA/1 sectors, 8K
vocoding, BP=1%)
Up to 48
Ports
to BTS
to PSTN
48 E1
64 E1
SS7 Port Capacity
Up to 16 links
Switch network
T-switch (3K*2K)
Power Requirements
Primary
Back-up
DC -48V (-43V ~ -55V)
DC –48V (-43V ~ -55V)
Environmental
Requirements
Temperature
Humidity
0~50oC
0~90%
Space Requirements
750(W)*700(D)*1886(H) mm (MTU inside)
18
BSC (R2/No.7) Capacity
Item
Subscriber traffic at busy hour
Average Call Holding Time
BHCA per subscriber
Blocking Probability (GOS)
Call Processing Capacity
Traffic Handling Capacity
The Number of Subscribers Accommodated

Capacity
0.1 Erlang (originating + terminating)
90 sec.
4 BHCA/Sub.
1%
130,000 BHCA
Max. 1,892 Erlang
18,920 Subscribers
Performance value above is call processing capacity of half call
(originating : terminating = 50:50) in view of only voice call
processing without considering effects of authentication and mobility
(location registration, paging, softer handoff).
19
BTS
20
BTS
BTS Types

Indoor BTS (Standard type)
up to 8 FA available.
3 sectors/FA available.

Outdoor BTS
up to 4 FA available.
3 sectors/FA available.

Micro/Pico BTS
3FA/1FA (omni)
BTS Key Feature



Various type of products
Macro Indoor/Outdoor, Micro, Pico
Coverage Extension
Meet various user need
Compact Design
Lower equipment cost
Easy transportation
Less installation space
Enhanced Maintainability
Inventory function
Built-in test/measurement set
Remote restart control
BTS Block Diagram
(1)
BHI (Back-haul Interface)



(2)
Provides communications path for IPC nodes.
Packet routing for control and traffic data.
Provides interface to the BSC.
CCB (CDMA Channel Bank)




Call Processing.
Digital signal processing for each CDMA channel.
Combines base-band signal for forward link and distributes base-band
signal for reverse link.
Converts digital to analog signal for interworking with RF or vice
versa.
21
Fig.
BTS Block Diagram
(3)
RFU (Radio Frequency Unit)


RF Control Function
for TX path
converts frequency up for transmit signal (UDC).
-

(4)
amplifies transmit power (HPA/LPA).
filters transmit signal (TX Front End).
for RX path
provides space diversity with 2 RX antenna per sector.
-
filters signal received from antenna (RX Front End).
-
amplifies received signal with low noise (LNA).
-
converts frequency down for received signal (UDC).
TFC (Timing & Frequency Control)


generates and distributes system clock from GPS (Global Positioning
System).
collects alarm about H/W and environment and reports.
22
BTS Capacity

Under fixed-to-fixed radio condition at 0.1 Erlang/subscriber
Item
Capacity
The number of traffic channels per sector
(without soft handoff)
8K vocoding
Up to 40 channels
13K vocoding
Up to 23 channels
Traffic capacity per sector using 8K
vocoding
BP = 1%
29 Erlang
BP = 2 %
30.9 Erlang
The number of subscribers per BTS
(1FA/3 sector)
BP = 1%
870
BP = 2%
930
The number of RF channels per BTS
(1 RF channel = 1.25 MHz)
Up to 8
BTS Specification

Frequency Band
800 MHz (TIA/EIA IS-97).
1.8/1.9 GHz (ANSI J-STD-008).

Channel bandwidth
1.25 MHz.
# of Sector per FA
Omni or 3 sectors.
Channel Element
6 MCPAs/FA (3 sectors).
16 CEs/MCPA
Output Power (TX)
16W/sector, 20W/omni in 800 MHz (LPA type).
12.5W/sector, 16W/omni in 1.8/1.9 GHz (HPA type).



23
BTS Configuration (Standard Type)
Fig.
24
Subscriber Unit
MS (Mobile Station)
Fig.


A portable unit that has a self contained data capabilities.
Provides external interfaces for data services
-
RS-232
Desktop
Fig.


A fixed subscriber unit that has a self contained data capabilities.
Provides external interfaces for data services
-
RS-232
25
SSU (Single Subscriber Unit)
Fig.


A fixed unit with a standard wireline interface
RJ-11
Standard telephone
G3 fax (optional)
Provides external interfaces for data services
RS-232
MSU (Multi-Subscriber Unit)

A fixed unit with multiple subscriber interfaces.

Provides max. 32 subscriber interfaces using 4RF.

Available in 1Q, 1999.

Definition
O&M

Provides information and environment to make use of call
handling and various functions in maximum through BSM.
Function
-
S/W and Database Downloading.
-
Fault Alarm Indication and Maintenance.
-
E1 Link Control and Maintenance.
-
Subscriber Line Control and Maintenance.
-
Test Function.
26
O&M Configuration

Initialization

Downloads S/W (OS, loader, application, PDL) to the system.
Fault Management

Detects, isolate and recovers faults.
Configuration Management

Manages data for the system configuration.
Security
-

Make sure of the system security from the illegal access to the
system.
Performance Management
-

Collects data for the evaluation of utilization and performance
of the overall system.
Accounting (R2/No.7 only).
-
Collects charging data and evaluates.
Accounting (R2/No.7 only)

Collect call detail records generated for usage of resources.

Transfers accounting information to the billing center or OMC over
X.25 in need.
BSM Specification
Item
Product Name
CPU
Main Memory
Cache Memory
Graphic User Interface
Operating System
Hard Disk
Interfaces



Capacity
SUN UltraServer Enterprise 2
Two 200 MHz UltraSPARC CPU
256 MB
32 KB Cache Memory
2 MB External Super Cache per CPU
X-WIN Motif 2.x
Solar is V2.x
4.2 GB Internal Hard Disk
Interface between WLL Network and PSTN
V5.2 or R2/No.7 over E1/T1.
Air interface
TIA/EIA IS-95A for 800 MHz frequency band.
ANSI J-STD-008 for 1.8/1.9 G frequency band.
Interface between BSC and BTS
LGIC’s proprietary protocol over E1/T1
27


Interface between BSC and BSM
LGIC’s proprietary protocol over RS-422.
OMC interface
TCP/IP over X.25
Network Configuration
Network Option

Option 1 : V5.2
Network Access Point
Concentrated trunk interface (ETSI V5.2, ITU-T G.965)
Central office concentration
Call features support in CO

Option 2 : R2/No.7
Network Access Point
Signalling Point
Tandem office connection
Supplementary call features support at WLL.
Evolution


Higher Speed Data (IS-95B)
64 kbps packet interface unit and external IWF.
Medium rate data vocoder.
IS-2000
IS-2000 (1x) Air Interface
28