Analysis of service access capability of GSM network after upgrading to GPRS

Summary

Starting from the analysis of GSM spectrum efficiency, this paper analyzes the loss of spectrum efficiency of voice service after the GSM network is upgraded to GPRS, and the new data service access ability, and finally takes into account the maximum access ability of the integrated service under GSM current spectrum from the mutual substitution between voice and data service access ability. GPRS network planning has a quantity of guidance significance.

In order to meet the demand of high speed mobile IP service, GSM standard organization has developed packet wireless data Service--GPRS, it can not only provide 9.05~171.2 kbit/s variable rate on wireless channel, but also realize packet transmission on wireless channel, and introduce packet network in existing circuit switching network, It provides the important network platform for GSM operators to expand the service area of integrated information services by providing voice service, and lays the foundation for the GSM network to the third generation evolution. After the introduction of GPRS, the M-Net is based on the traditional voice access, it provides the access of packet data, and the analysis of the integrated service access ability of voice and data under the current spectrum is advantageous to the synchronous development of the service and network in GPRS upgrade, thus providing a reasonable theoretical guidance for the planning and design of GPRS large-scale application. (Computer science)

Analysis of GSM voice frequency spectrum efficiency under 1 existing spectrum

The spectrum efficiency of GSM cellular system is defined as the amount of traffic or the number of users that can be accommodated per unit area unit band, respectively, Erl (km2 MHZ), or the user/(km2 MHZ), which is an important index to measure the service access capability of communication system. The spectrum efficiency of GSM cellular system can be expressed as modulation efficiency ηm. And the product of multiple access efficiency ηma is η=ηmxηma. Among them, ηm= (B/BC)/H/BNA=H/BCNA: The total bandwidth (MHz) available to the b--system, bc--voice channel bandwidth or channel interval (MHz), h--per channel traffic (ERL), number of cells in the n--cluster, a--area km2).

Ηma access efficiency depends mainly on the ratio of business channel and public control channel, GSM can reach 0.9.

(1) Conventional 4x3 frequency multiplexing mode

H for the 0.7ERL/TCH,BC 0.025MHz, the conventional 4x3 cell multiplexing lower n value for the 12,a in the hexagonal cellular structure area for the 2.6R2/3, at present, the urban base station space between the general can reach 5mm, that is, d=5mm, can calculate the cell radius r=d/3 =500/1.73=289m.

According to the above values, the speech spectrum efficiency of GSM cellular system can be computed: η=0.7x0.9/(0.025X12X2.6X0.5X0.5/3/3) =29.1erl/(km2 MHZ), with an average per-user busy time of 0.02Erl of traffic, the unit area per unit of the number of users can accommodate 1454 households/(km2 M-ratio).

(2) Use of MRP, 1X3, IU0 and other frequency multiplexing mode

The frequency multiplexing degree of MRP compact frequency multiplexing can reach the frequency multiplexing of 7x8,1x3 frequency multiplexing, and the frequency multiplexing degree of 7,iu0 intelligent Concentric circle technology can reach 8~10.

At present, most of the online use of MRP close frequency multiplexing and 1x3 frequency multiplexing mode, in order to calculate the frequency of close reuse after the spectrum efficiency, the desirability of 8, then η=29.1x12/8=43.6erl/(km2 MHZ), with an average per-user busy time of 0.02Erl of traffic, the unit area per unit of the number of users can accommodate 2181 households/(km2 MHZ).

China Mobile After the analog network back to the net spectrum width of 29MHz, the current GSM network can access the maximum traffic density of 1265 erl/km2 (using tight frequency multiplexing mode), the maximum user density of 63242 households/km2.

The above analysis is only for macro-honeycomb, when the use of micro-cellular mode, because of the more intensive frequency reuse, if the network carefully planned, some areas of traffic absorption will exceed the above analysis value.

The loss of GSM voice spectrum efficiency and the efficiency of data service spectrum after the introduction of 2 GPRS

GSM network upgrade to GPRS, in the Wireless Interface data Service channel allocation mode can be fixed allocation, full dynamic allocation, fixed and dynamic distribution of the combination of three ways. At present, the handset support ability is iu+3d, 1U+4D, if the Wireless Interface data Service channel allocation way uses the fixed and the dynamic Allocation Union way, namely GPRS upgrades each cell fixed allocates one data service channel, 2~3 the service channel according to the network traffic situation uses the dynamic allocation way, It can calculate the loss of speech spectrum efficiency and the new data service access ability.

Based on the current network base station commonly used configuration S6/6/6, a total of 6 carriers per cell 44 tch channel, the definition of one tch as PDCH, then each cell voice channel loss for 1/44=2.3%, the traffic loss of about 2.3%.

The following analysis each cell fixed 1 data service channel, according to network traffic situation 2~3 a business channel uses the dynamic allocation method, the new data service access spectrum efficiency.

Because the GPRS access service occupies the wireless network resources and the circuit business is comparable, so the traffic volume of its access can be equivalent to that of the circuit business, and its access ability can be estimated by ERLANGB formula. When the dynamic allocation method is adopted, the voice channel is assigned high priority, the packet data is low priority, the GPRS Access data Service fully utilizes the "surplus" time slot of the voice service, the maximum traffic value of each GSM channel access can be 0.7 erl/channel, The amount of voice traffic that the network is currently accessing is the business volume of the data business, then the network can be used for gphs egprs=ntotx0.7-a, in the type, EGPRS for GPRS available, Ntot for the total number of business channels in the community, a for the community access voice service traffic.

In the case of adopting CS-1 and CS-2 coding ratio of 2:8, using iu+3d mode, the average theoretical data rate can reach kbit/s when the 3 o'clock gap is bundled, and the average theoretical data rate per time gap can reach 10.7 kbit/s, considering certain data retransmission rate and TBF establishment time, The actual data rate per time slot is about rb=4~5kbit/s, and the value is 4kbit/s. If the data business spectrum efficiency is defined as the amount of data or the number of users that the unit Area unit band can hold, the units are kbit/(s m2 MHZ) or the user/(km2 MHZ). Analog speech spectrum efficiency can deduce the data service spectrum efficiency of the GPRS cellular system under conventional 4x3 multiplexing Ηb=egprsxηmaxrb/bcna= (ntotx0.7-a) XRB/BCNA, the data Service spectrum efficiency of the compact frequency Multiplexing Gpbs cellular system η2=η1x 12/8=1.5xη1.

3 Voice and data service access capability under comprehensive consideration of existing spectrum

Obviously, the above analysis is based on condition I. The frequency spectrum efficiency of voice access is maximal; condition two, each cell fixed allocates one data service channel, according to network traffic situation 2 service channel uses the dynamic allocation way; condition three, each user busy time data quantity takes 180 kbit/s; condition four, each user busy time traffic volume takes 0.02 The results of erl and other conditions. In this paper, we still analyze the integrated service access capability based on condition two and conditional three. Each redundant H voice service has not reached the 0.7 erl/tch, the data access ability obviously increases, which shows the substitution effect between the voice access ability and the data access ability. Table 1 for China Mobile MHz bandwidth, different voice access and data access ratio of GPRS network integrated access capability (using tight frequency multiplexing technology), at this time, 900MHZ and 1800MHz frequency band simultaneously upgraded to GPRS.

With the wide use of GPRS, the improvement of terminal data capability and the development of various services, wireless interface channel allocation mode, data business model will change, the whole analysis based on the conditions will also change, the conclusion will be different.

4 Conclusion

This paper only theoretically analyses the loss of spectrum efficiency and the new data service access ability of the voice service after the GSM network is upgraded to GPRS, calculates the maximum access ability of the integrated service under the existing spectrum of GSM network, and the method and practicability still need to be validated further. But based on the current traffic and data business model calculation results of the current GPRS network planning has a number of guiding significance.