The influence of GPRS on GSM network resources

As a new technology and new service introduced in the network, the implementation of GPRS will certainly affect the existing GSM network resources which are based on voice. In addition, because of the different characteristics of GSM voice service and GPRS data service, the influence of network specific function on them is different, Therefore, in the network planning should give GPRS data and GSM voice different attention and treatment, this article will do some discussion and research.

Characteristics of GPRS Data service

GPRS as the carrier of mobile data service, it can attract users the most important reason is to provide different needs of data services, such as: www business (Internet surfing, chat room, online translation), WAP business (WAP mail, WAP access), e-Business, E-com-merce Business ( Online Banking, online stores, stock inquiries, remote information (telematic) Business (location tracking, traffic information), Life and leisure business (hotel inquiries, travel information).

Different data service characteristics are different, for example, the WWW business data packets and data volumes are usually much larger than WAP business.

In addition to the variety of data services, data business users are also different. For example, business users (busi-ness subscriber), midrange users (Mixed subscri-ber), and private subscriber, differ greatly in the amount of data required for different data services. For example, business users have a much larger demand for the WWW business than private users, but the demand for WAP services is similar.

The distribution of users is another important factor that affects the distribution of network traffic. The distribution of GPRS users at different levels is not the same, for example, business users are mainly concentrated in the urban areas, while private users are a large proportion of residential areas. (Computer science)

It is obvious that GPRS data traffic is much more complicated than GSM voice traffic, it is GPRS data service type, data user level and user distribution synthesis. In different areas of the GPRS data volume is different, so the GPRS wireless network capacity and GPRS wireless coding Scheme (cs:coding scheme) requirements are different, such as high traffic Volume business center area needs high coding scheme CS4 and more GPRS wireless channel, These are the factors that should be considered in the actual network planning.

The influence of GPRS on network resources

The GPRS data service needs to use the network resources and the mutual influence with the GSM voice telephone service, therefore how to use the network resources reasonably effectively between the GPRS data service and the GSM voice service, is an important topic which introduces GPRS.

GPRS network Wireless Link quality-load-dry ratio (c/i) directly determines the GPRS data transmission rate, while the frequency of wireless network is the most direct determinant of load-dry ratio, the most important aspect of frequency use is the choice of frequency multiplexing. According to GSM05.50 can be known in the TU3 test environment to achieve the GPRS network frame deletion rate (Bler) less than the 10%,CS2 need to load dry than 15.5db,cs4 need to load dry than 20dB. Therefore, according to the simulation results can be known under different CS conditions to meet the network area:

· When the CS2:3/9 is reused, the region loading ratio of 25% is less than 15.5dB, that is, the frame deletion rate is greater than 10%;4/12, the value drops to 12%

· When the CS4:3/9 is reused, the region loading ratio of 48% is less than 20dB, that is, the frame deletion rate is greater than 10%;4/12, and the value drops to 30%.

It is well known that GPRS data service needs more relaxed frequency multiplexing than GSM voice service to guarantee the load-dry ratio of wireless network and improve the data transmission rate of GPRS. Therefore, in the GPRS network, we should provide different frequency multiplexing degree for two kinds of service. In addition, it is necessary to note that the GPRS dynamic channel, which can be used by both the data service and the voice service, is helpful to the capacity of the wireless channel. However, dynamic channel also means the "waste" of frequency resources in a sense, because these high multiplexing frequency points are occupied by the low demand voice service, for example, the voice service needs only 3/9 multiplexing but occupies the 6/18 multiplexing frequency point of GPRS programming, this problem is more obvious in the GPRS data load hour.

In addition, the impact of FH on GPRS data service is more complicated than that of voice service. After analysis we can get the following conclusions:

• The higher the coding scheme, the smaller the frequency hopping gain.

• Lower-load users (using coded CS1 and CS3), and frequency hopping can provide positive gain when required for small bler.

• High-load users (using coded CS4 and CS3), frequency hopping only brings negative gain.

The use of power controls can also affect the distribution of load-dry ratios in wireless networks:

• The power control can average the load-dry ratio of the network, that is, the number of users with low load ratio and Gao Cai dry ratio decreases, while the number of users in medium load-dry ratio increases.

• In networks that allow encoding schemes CS1 and CS3, the power control can improve the data rate; In the case that the encoding scheme is CS4, the user with high data rate of CS4 can reduce the Wireless Link Control option It is an important work that the GS purpose channel is used as GPRS capacity and the voice business capacity is not affected. According to the simulation, the GPRS channel load rate is a very critical factor affecting the service quality of the data Services (Quality of Ser-vice), when the GPRS channel load rate reaches 85%, the data transmission rate of GPRS users will drop dramatically. And the response time of the network to the data business will rise sharply.

GPRS wireless network Capacity planning is an important, but also challenging job. For now, there are several difficulties to be addressed:

· GPRS Data's business diversity makes GPRS capacity planning more complicated.

• The GPRS capacity planning method has not formed a unified consensus, different methods of calculation principles, the results of the calculation is far from the difference.

· GPRS user's word traffic model is not very accurate.

• As part of capacity planning, GPRS signaling load and signaling channel capacity planning.

The influence of GPRS on dual-frequency network

GSM900 and DCS1800 dual-frequency network generally have three kinds of network structure, respectively: 900MHz base Station and 1800MHz base station using independent BSc and independent Msc;900mhz Base station and 1800MHz base station using independent BSC but co-MSC 900MHz Base Station and 1800MHz base Station co-BSC, Total MSc.

The most common existing dual-frequency network is the first structure, because the 900MHz and 1800M base stations in the same location repeated coverage and belong to different Lac location area, so for the GPRS mobile phone, may be frequent routing area updates and cell re-election. In the other two dual-frequency network structures, the routing area is updated in the LAC location area or the RAC routing area boundary according to the configuration. This frequent routing area renewal and the cell re-election to the mobile phone GPRS performance will have what effect?

GPRS mobile download data from the mobile download rate (throughput) changes in the trend can be seen, when the mobile phone to be re-election must stop the transmission of data, waiting to complete the cell re-election after the resumption of transmission, during the suspension of data transmission for about 3 seconds; when the mobile phone to update the routing zone must stop transmitting Wait for the routing area update to resume delivery, during which the data transfer pause lasted about 15 seconds. Therefore, frequent cell re-election will obviously reduce the average rate of data transfer, while frequent routing area updates can worsen this index more seriously. According to test statistics experience, download a 2M large file, under normal circumstances, if 3 times routing area update, the average rate will be reduced by about 12%.

What is the difference between district re-re-election and routing area update under different network structures? In fact, routing area update (routingareaupdate) or community update (cellupdate) differs greatly in different network structures, and it will naturally have a distinct effect on GPRS data transmission.

Like GSM voice service, building a good network must first understand the user behavior and traffic model in the network. GPRS brings the rich and colorful data application, but also brings the difference and complexity of network resource allocation and network planning. Network wireless frequency resource multiplexing and FH, power control and other Wireless Link control options are necessary for the application of GPRS special processing, such as different network regions will use different GPRS coding scheme, then these places to use the choice of frequency hopping will be different In addition, the wireless capacity of GPRS data Service sharing channel resources with voice service is also an important factor affecting the overall network performance. On the other hand, we find that the network structure of GPRS network has direct influence on GPRS network performance (signaling load, data rate).

In a word, in the actual network, it is necessary for us to treat the traditional GSM voice service and GPRS data service in different and comprehensive consideration, and the final goal is to make the network resources get the most full and effective use.