7 OMP121000 GPRS EDGE Build-In PCU Radio Network Planning ISSUE1.00

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GPRS EDGE Build-in PCU Radio Network Planning















There are 6 steps for the GPRS capacity planning:

Calculate the average bearing rate over the IP layer according to the data rate of each

coding scheme and the ratio of each coding scheme to the overall coding schemes.

Calculate the bandwidth of each GPRS channel.

Calculate the traffic volume per GPRS MS in busy hours.

Calculate the maximum number of MSs per cell as follows:

Determine whether the CS services and PS services are limited under a certain

number of MSs.

Use the double Iterative algorithm to calculate the maximum number of MSs in a

cell.

Calculate the number of PDCHs occupied by GPRS services.

Calculate the number of static and dynamic PDCHs required by actual GPRS services.









Considering the IP rate, if RLC is NACK mode, then LLC normally is not NACK mode, so the

retransmission rate on LLC layer should be considered. And the bandwidth consumption of

retransmission on LLC layer is usually greater than that on RLC/MAC layer. So NACK mode

on RLC layer cannot enhance the bearing rate of IP layer compared with ACK mode.



Where,「」means round up, 『』means round down.

The system transmit one radio block every 20ms.

If the required bearing rate of physical layer on Gb interface is VGb for each PDCH:

Suppose the frame format of Gb interface is: IP data+H2 bytes

VGb＝Ri× (IP data+H2) / IP data = Ri ×(320＋53) / 320＝1.166V_IP

This result is almost decided by the average length of IP block, whose

typical value is 320.



Generally, the data rate should be calculated according to the traffic model.

Hereunder provides assumptions and facts for data rate calculation.

The following assumptions can be made:

1) The SNDCP (SubNetwork Dependent Convergence Protocol) is not compressed and

decompressed, and is not segmented and reassembled. (Such an IP packet is transferred as

an LLC PDU across the LLC layer.)

2) LLC performs transfer with unacknowledged mode.

3) The format of an LLC frame is: LLC header (9 bytes) + SNDCP header (4 bytes) + IP data +

FCS (Frame Check Sequence, 3 bytes). Each data packet seizes a RLC length indication byte.

4) RLC performs transfer with acknowledged mode and 10% of retransmission rate is

considered.

5) An IP packet is 320 bytes in length in average.

6) IP data flows continuously within 10 IP packets at least.

7) A radio block is transmitted every 20ms.

Hereunder lists the facts for the data rate calculation:

Generally, a RLC/MAC header seizes 3 bytes. If tail bits are not considered, the LLC PDU

bytes can be transmitted in each RLC data packet is 20 under CS1 (Channel Coding

Scheme), 30 under CS2, 36 under CS3, and 50 under CS4.

For the transfer performed with RLC acknowledged mode, the transfer of an LLC PDU

means a TBF establishment and release procedure. Generally, during a TBF establishment

and release procedure, the overhead of the RLC/MAC control blocks account for 20% of

the total radio blocks. This overhead includes the time for TBF establishment and release.

The protocol headers of FR, NS, BSSGP, LLC, and SNDCP across the Gb interface total 53

bytes.



For CS1, CS3 and CS4, the results are 5.73 Kbps, 10.3 Kbps and 14.4 Kbps.













Through altering PDCH Channel Multiplex Count, you can adjust Each "GPRS Channel"

Bandwidth until it is close to the expecting minimum bandwidth of customer.

Span: [1/maximum time-slot multiplex capability of MS, 8]

















The valid coverage area is subject to two parameters: signal-to-noise ratio (C/N) and signal

strength. C/N determines the signal transmission quality (bit error rate BER or block error

rate BLER). The coverage area analysis is based on the similarity between the two

parameters in the GPRS system and the two parameters in the GSM system.

For different coding schemes on the same channel, the BERs are different. For the same

BER on the same channel, the coverage areas under different coding schemes are different.

The BER performance mentioned later refers to the BLER.



When the BLER in CS1 coding scheme is lower than 10%, the requirement is the same as

the C/I requirement of voice quality level 4.

When the BLER in CS2 coding scheme is lower than 10%, the requirement is the same as

the C/I requirement of voice quality level 3.

Therefore, you can analyze the GPRS network coverage based on the existing GSM

network coverage and voice quality. In CS1 coding scheme, the coverage area of the GPRS

network is almost the same as that of the GSM network. In CS2 coding scheme, as the C/I

is improved, the coverage area of the GPRS network is about 80% of that of the GSM

network.



For link budget, the requirements on receiver sensitivity in GSM are as follows:

BTS: -104dBm

MS: -102dBm

Note:

“*” indicates that the PDTCH/CS-4 cannot meet the service standard required

by the transmission condition.

TU50 stands for typical urban area, 50km/h; FH stands for frequency hopping,

RA250 stands for rural area, 250km/h; HT100 stands hill terrain, 100km/h.



Note:




RA250 stands for rural area, 250km/h; HT100 stands hill terrain, 100km/h.







Note:

“**” indicates that for service quality, BLER < 30%.




RA250 stands for rural area, 250km/h.

The correct training sequence requirement is 1) stands for one training

sequence; 2) stands for 3 training sequence; 3) stands for that the requirement is applied

to CPRACH.





























Normally GPRS/EDGE MS use the same cell selection and reselection strategy as GSM，mostly GPRS/EDGE network do not implement NC2。



If the quality of the GPRS/EDGE services on the GSM1800 network is low because of the

poor coverage of the GSM1800 network, you need to improve the coverage planning for

the GSM1800 network or change the strategy of the GSM1800 preferred.











Documents

7 OMP121000 GPRS EDGE Build-In PCU Radio Network Planning ISSUE1.00