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ZXG10 HR Solution

2005-03-16

There are several kinds of voice encoding schemes in GSM protocol,such as FR, EFR, HR and AMR. The lack of frequency resource is a big

problem with the GSM network development. In order to expand the

network capacity with current frequency resource and little hardware

investment, domestic and overseas operators have issued HR in their

schedules.

1.Principle of HR

GSM is a TDMA-based system. Each radio frequency consists of eightTime Slots (TS ), ranging from TS0 toTS7. Each TCH multi-frame

comprises 26 frames with the period being 120ms. The 13th frame is

SACCH and the 26th frame is an idle frame.

When the system adopts Half Rate Speech and Data, the frame structure

at air interface is the same as that of FR. The odd frames of the multi-

frame are assigned to one subscriber and the even frames of the multi-

frame are assigned to another. The 26th idle frame is assigned to beSACCH of the second subscriber. So, one TCH/F changes to be two

TCH/Hs; the TCH quantity is doubled and voice quality declined.


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HR scheme adopts VSELP algorithm and the coding rate is only

5.6kbps.Campared with 13kbps data rate of FR scheme, the voice

quality of HR is not as good as that of FR. ETSI has made many tests to

verify the voice quality of HR, and the result is listed as follows:

2. HR Effects on the System

1. Effect on hardware and software

a) The Transcoder should support HR service.

b) The software of the system should be upgraded to support HR.

c) Capacity of BSC and MSC should be expanded to support the

increased radio traffic.

2. Load of main processor increases

For the same traffic load, the main processor (MP) load will be increased

by about 1%. The database table structure becomes more complex, and

HR related processing procedures and performance measurement

counter have been added.

3. Radio network indexes

a) Network congestion will be reduced. For those heavy traffic areas thechannels in this cell will be increased by properly configuring HR

service, which can greatly reduce the congestion in this cell.

b) The network coverage range remains unchanged.


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c) The subscriber assigned to HR channel will be given reduced voice

quality.

3. ZXG10 HR Solution

MS access to FR/EFR or HR channel

ZXG10-BSS system will automatically detect whether the terminal

supports HR service or not, and assign corresponding HR or FR/EFR

channel according to parameters like priority level.

Handover between FR/EFR and HR channels

In ZXG10-BSS system, the handover between HR channels or betweenHR channel and FR/EFR channel is supported. The assignment is based

on the concrete situation of the network and the channel assignment

priority level.

Channel allocation in BSC

Besides adding HR service, there are TCH/H channel and TCH/F

channel in cells, and FR/EFR circuit group and HR circuit group in the

A interface circuit group. Therefore how to allocate these resourcesbecomes very important. The ZXG10 provides a comprehensive channel

resource allocation method, to ensure the efficient use of system

resources.

The system allocates HR or FR/EFR resource according to users

priority level, which is given by MSS.

The system can configure HR and FR/EFR channel according to

relative parameters. For the terminals supporting HR, they will take

priority for corresponding HR or FR/EFR channel according to theparameters.

The TCs used for HR also support FR/EFR. If TCs used for FR/EFR

are exhausted, the system will allocate TCs of HR to FR/EFR service. If

TCs used for HR are also exhausted, the system will allocate FR/EFR

channel instead of HR resource, until TCs for HR are available.


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By using HR service, the number of channels in each cell is

increased. This number can be doubled if all channels work in HR mode.

Users have to add SDCCH along with the increase of channel numbers.

Supporting for Multi-frequency HR

ZXG10-BSC and ZXG10-BTS support frequency configuration in

850M, 900M (including EGSM), 1800M, etc. The HR service for all

frequency ranges will be provided together.

The system provides parameter configuration for HR service which

supports multi-frequency, so as to ease the configuration.

Measurement counter

Numerous counters have been added to support HR service. Once the

corresponding measurement task gets started, the system can record the

value of all counters in predefined period. More than 100 TCH/H

counters are provided for further network analysis and report output,

including number of available TCH/H, number of seized times, number

of call drops, total busy hours, number of handover attempts, number of

handover successes and handovers between TCH/F and TCH/H.

Dynamic HR

This function provides intelligent HR and FR/EFR channel

conversion. When user sets the decision threshold for channel

conversion in OMCR, the system will automatically adjust the number

of HR channel and FR/EFR channel in the Abis interface if condition is

satisfied.

Method and procedure

A dynamic HR software module has been added in the MP. The

system detects all cells supporting HR function, and informs

background to convert data in case of satisfied condition.

User configures dynamic HR parameter for cells and the parameter

will take effect immediately after being set.


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The OMCR implements configuration channel conversion

according to the messages from BSC MP. The converted data takes

effect immediately.

When the BSC MP detects the requirement of channel conversion

again, it will inform OMCR and repeat steps above.

ZXG10 HR solution can increase the radio capacity of the existing

GSM network with no investment on radio resource and little investment

on system update. Therefore, it will be widely used by operators

worldwide. (Zhang Kai)

Previous:ZTEs Solution and Evolution Strategy for Optical Network

Next:Introduction to ZTE Mobile Division

ZTEs Solution and Evolution Strategy for

Optical Network

2005-03-16

1.Introduction

With the development of the telecommunications industry, operatorshave changed their attention from blindly pursuing greater network

capacity and broader bandwidth to the financial indexes, such as

CAPEX, OPEX and ROI, the cost performance of system equipment, the

multi-service solutions, and the functionalities of intelligent deployment

and dispatching that help save more labor costs.

Generally speaking, optical networks are basic networks. So an optical

network will bear higher service pressure once services increase. It canbe said an optical trunk network demands broader bandwidth and greater

capacity, and an optical metro area network pursues more services and

better flexibility. So far the available bandwidth of global optical trunk

networks has been going saturated, and even overmuch, and operators

investment in optical trunk networks keeps stable or decreasing.
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However, ultra-long haul transmission has attracted great attention

because of urgent practical demands. Some of its key technical problems

have been solved, and its commercialization is quickened.

In addition, data services including Storage Area Networking (SAN)services are emerging, and image and multimedia services have great

potentials and bright application future. Many operators are striving for

becoming a Multi-Service Operator (MSO). The hand-in-hand

development of voice, data and image services makes the term "Triple

Play" glaring. Operators are devoting themselves to the construction of

metro area networks. Their true goal is to implement network

optimization, and to avoid "faults" between the trunk backbone network

and the access network.

In general, an optical metro network is a bearer of the metro service

network. If the optical network such as traditional SDH and WDM can

only transfer service signals simply, the pressure on the service layer

will be very high.

Nowadays, both old operators who have modified their networking

strategies and emerging ones choose next generation SDH or metro area

WDM technologies and service layer equipment to jointly build theirnetworks.

ZTE Corporation thinks that next generation SDH has great vitality, and

that "SDH is degenerating from a system to an interface" is a too early

opinion. Next generation SDH has two strengths: multi-service and

intelligence. Evolution from SDH to MSTP represents multi-service,

while intelligence means GMPLS/ASON control planes are used to

implement flexible bandwidth allocation, automatic end-to-end service

dispatching and dynamic protection and restore functions. WDM has allalong been asked to just have large capacity and transparent transport.

However, under new circumstances, new generation WDM equipment is

asked to provide quick service access and optical layer protection

besides large capacity, broad bandwidth and high service transparence.


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2.System Equipment

World famous optical communication system vendors all provide

DWDM systems with super capacity and ultra long haul transmission

capability. ZTE makes no exception.

ZTEs DWDM system can support multiple service interfaces such as

SDH, SONET and GE. Its capacity can be smoothly upgraded from 400

Gb/s to 800 Gb/s, and even to 1.6 Tb/s. Its wavelength range covers C+L

wave bands. It can implement beyond 5000 km transmission through

optical fibers G.652 and G.655 without any electric relay. The involved

technologies include mixed amplification of distributed Raman and

EDFA (Erbium-Doped Fiber Amplifier), super out-band FEC (Forward

Error Correction), NRZ (Non-Return to Zero) and RZ modulation codes,

dynamic power equalization, distributed dispersion management.

The distributed Raman amplifier has such characteristics as great gain

bandwidth, gain flatness, and automatic gain spectrum adjustment

according to signal distribution. Just due to its engineering experience in

ultra long haul WDM transmission, ZTE was granted the right to draft

G.665, a new standard for the Raman amplifier at ITU-T SG15 (optical

and other transfer networks) in October, 2003. Now the standard hasbeen approved.

With the maximum bandwidth of 400 Gb/s, metro WDM equipment

provided by ZTE can offer multi-service OUT, T-MUX, optical

multiplex section protection ring and optical channel shared protection

ring. It is noticeable that ZTEs metro WDM equipment has the most

complete protection switching structure, best protection switching

performance and most reliable protection switching ability, which is

second to none in the industry.

The combined design of serial/parallel optical switch is used for ZTEs

metro area Optical Add/Drop Multiplexer (OADM) equipment. Making

use of ZTEs unique "upgrade interface", the metro area OADM


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equipment can truly ensure "online upgrade" without interruption of

services in use.

Moreover, according to the application situation of metro area access

networks, ZTE has, following G.694.2 and G.695, new ITU-T standards,launched its compact Coarse Wave Division Multiplexing (CWDM)

equipment with high cost performance. It can provide users with quick

capacity expansion and network optimization capabilities.

Based on SDH, ZTEs Multi-Service Transport Platform (MSTP)

equipment can implement multiple rates, including 155 Mb/s, 622 Mb/s,

2.5 Gb/s and 10 Gb/s. On one hand, the MSTP retains the cross-connect

capability inherent in SDH and traditional SDH/PDH service interfaces

to keep meeting demands of Time Division Multiplexing (TDM)

services; on the other hand, it also supports ATM, transparent

transmission on Ethernet, Ethernet L2 switching, Resilient Packet Ring

(RPR) and Multiple Protocol Label Switching (MPLS) to meet demands

on convergence, combing and consolidation of data services.

ZTEs MSTP first uses GFP to ensure excellent encapsulation. In

addition, its virtual concatenation and Link Capacity Adjustment

Scheme (LCAS) is adapted to diversified bandwidth granularity and canmake link capacity adjustment in a certain range. Besides Ethernet

functions, its RPR functional module has overcome the shortcoming of

slow switching of Ethernet and has implement quick protection

switching in 50 ms. The RPR also provides fairness algorithm to

guarantee reasonable utilization of link bandwidth and furthest avoid

link congestion. With MPLS functions, the networking can be extended

from ring to grid. PW is used to implement multi-service access and

convergence at the user end, while by the tunnel are data converged into

the core data network. In this way, all-way and all-network MPLS is

finally implemented, which can bring the strengths of MPLS into full

play.

The private line/network service for key clients is always an important

source of operators earnings. The MSTP equipment helps implement its


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point-to-point, point-to-multipoint and multipoint-to-multipoint

networking, develop VPN services such as EPL, EVPL, EPLAN and

EVPLAN, and provide proper CoS and QoS according to clients

requirements. In particular, L2 VPN (Virtual Private Network) (such as

Virtual Private LAN Services) that makes use of MPLS functions has amuch better cost performance than the traditional TDM private line.

3. Evolution Strategies

For a long time, traditional optical networks may only implement

transfer, multiplex, cross connection, monitoring and survivability of

signals on the user layer. They dont have the switching functionality, so

they are less intelligent, i.e., traditional optical networks do nothing with

"intelligent networks". When service layer networks are reviewed,

"switching" is found the basis, no matter in fixed networks or in mobile

networks. Accordingly, without the concept of "dynamic switching",

intelligence is not intelligence.

Therefore, the introduction of "dynamic switching" into traditional

transport networks is a historic breakthrough in the long-time concept of

transport networks as well as an important revolution in transport

network technology. However, the transport network doesnt have itsown signaling and routing protocols to support its intelligence. It has to

borrow related protocols of the fixed data network, such as GMPLS.

ZTE thinks that no matter for fixed switching networks, mobile

switching networks, fixed data networks, or optical transport networks,

the implementation of intelligence requires to introduce a control plane

or control entity into the networks. The core part of the control

plane/entity must rely on software, and it is implemented by multiple

signaling and routing protocols.

As for optical networks, equipment vendors may use their private

protocols to implement the control plane. However, private protocols are

barriers to interconnection of products from different vendors, various

sub-networks, different operation domains and diversified management


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domains. Therefore, it is completely necessary to standardize intelligent

optical networks. We have seen that it is just standardized protocols that

helped the large-scale commercial use of intelligent networks of PSTN,

GSM, GPRS, CDMA and CDMA 1x. Without globally unified

standards, it is impossible for any intelligent networks to be put intolarge-scale commercial use. Fortunately, now we can gladly see that

ITU-T is taking great efforts to make ASON standards, IETF (Internet

Engineering Task Force) developing GMPLS standards, and OIF doing

its best to make UNI (User Network Interface) standards.

Intelligent service-layer networks can directly provide end users with

services, such as online banking, automatic accounting cards, voice

mailboxes and prepayment. In the new situation, the service intelligentoptical networks can offer is bandwidth, if it can be regarded as a

service. They can provide bandwidth lease, wholesale, and so on. Of

course, they can also implement O-VPN and BOD services according to

users demands. Due to the special nature of optical networks, the

services they provide cannot be directly used by end users. But veteran

operators can provide such services to new ones; big operators can

provide them to small ones; and long haul operators can provide them to

metro area operators.

However, we still clear heads to understand that the early application

goal of intelligent optical networks would be to provide quick protection

and restoration when there are some troubles and to use standardized

signaling and protocols to implement "end-to-end service deployment",

rather than directly offer services.

Currently, physical connection, also called "hard connection" or

"permanent connection", is the only way to connect optical networks

with user-layer networks (including traditional PSTN switches, ATM

switches, IP routers and image processing equipment). In this way,

optical networks just mechanically transport signals from one end to the

other. Once such a bearer channel is established, it will keep stable in

several months, in half a year, in one year, or even in longer time.


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We can take the SDH network as an example. The permanent

connection of traditional SDH circuit deployment is implemented

actually by forced interference of the network management system,

which not only wastes time (that may be several days) and human

resources (that include a few experienced maintenance andcommissioning professionals), but also has low efficiency and is

difficult to change after the deployment is finished. However,

intelligence means "soft connection" between user-layer networks and

optical networks. A user-layer network should first apply to an optical

network for bandwidth it needs, and then the optical network will

quickly answer the application and provide an optimum connection

channel in time. Such connection can not only change the route

according to need, but also be demolished and rebuilt.

ZTE has developed ASON-based intelligent optical network equipment

with a goal to change traditional permanent connection into soft

permanent connection, and even into switching connection, to allow user

equipment to initiate a bandwidth application through UNI according to

its own need. ZTE deploys multiple functional units in the control part

of its intelligent optical network, including call controller, connection

controller, routing controller, protocol controller, strategy controller, link

resource management unit, finding agent and termination adaptor. Allcontrol parts have strict task division but cooperate closely to jointly

implement intelligent control functionality. Control units distributed to

different points communicate each other with I-NNI or E-NNI protocols

to quickly establish a connection channel and a bearing channel for the

service-layer network in a real time. It is no doubt that established

channels can be set free and demolished at any time, and be replaced by

new connection channels if they have some faults.

As for the network management system of the optical network, both the

transport plane and the control plane require its management. For

example, transmission impairments such as errors, jitter and drift of the

transport plane are reported to the network management system, while

troubles of the control plane such as troubles of the signaling network,


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call failure, connection failure and time-out also need reporting to the

network management system. Since the intelligent control layer is

added, "deployment management", one of the five management

functions of the network management system, may be weakened greatly.

ZTE adopts GMPLS as the main protocol of its intelligent opticalnetwork equipment. Besides, aiming at the characteristics of the optical

network, original MPLS architecture has been expanded in functionality.

And the signaling protocol prefers RSVP-TE, and the routing protocol

OSPF-TE and DDRP.

ZTE also thinks that existing user facilities in the network are working

maturely and stably, so it is unrealistic to rebuild them for the

introduction of intelligent optical networks. The solution is "intelligentagent". For example, a user device is connected to UNI-C via a simple

and easy-operating interface, and then the UNI-C is connected to the

intelligent optical network via a standard UNI-N interface. In this way,

the existing user devices will be changed least. So does the connection

between the traditional optical network and the intelligent optical

network. Generally speaking, it is a long-term revolution from existing

optical networks to intelligent optical networks. There is no way to

implement an intelligent optical network in a second.(YuanFei)

Previous:Santiago to Pioneer GSM wireless Local Loop (WLL) in Chile

Next:ZXG10 HR Solution
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