Discussion on the evaluation standard of GSM and CDMA wireless network

The purpose of the wireless network evaluation is to analyze the network running data and give a reasonable evaluation. Including the quality of network planning, network operation, network operation problems, hidden dangers, network investment utilization and other projects, and then fully grasp the overall operation of the network, for the further optimization and construction of the network to provide a direct reference.

In terms of GSM and CDMA networks, the two have corresponding evaluation criteria and methods. For the unification of the two system evaluation criteria, we can find out the corresponding relationship and get the unified standard from the system. This paper will discuss and explain the quantification of the unified standard of different system network evaluation from several important aspects of network evaluation. The evaluation of wireless networks is basically done around three aspects of coverage, capacity and quality. At this point, all systems are consistent, and the content and details of the wireless network assessment are described in detail below.

Network Coverage Assessment

For GSM network, the index of comprehensive evaluation network includes the absolute receiving level RX, which implies that the coverage level must meet the requirement of load-dry ratio (same frequency c/i≥9db, first neighbour-frequency c/i≥-9db), and for CDMA network, it comes directly from the Shannon formula of information theory, That is, directly measured by the load-dry ratio, including the front/back coverage status and the front/back link balance, the forward metrics include Ec/io, Rx, and reverse metrics including the cell phone TX.

It can be seen that the evaluation factors that influence the two kinds of system indexes are different, in order to evaluate the coverage characteristics of the two networks, the coverage evaluation of GSM absolute level can be compared with the evaluation of Ec/io and Rx of CDMA, and the corresponding coverage is achieved. (Computer science)

In the case of GSM, the coverage edge is defined as the receiving level (absolute value) rx≥-95dbm above, in which the same frequency c/i≥9db, the first adjacent frequency c/i≥-9db. Coverage definition: Coverage = (total number of RX≥-95DBM)/total number of samples x100%, while the CDMA overlay edge is defined as the receiving strength (loading/drying ratio) ec/io≥-13db,rx≥-95dbm above. Coverage definition: Coverage = (total number of EC/IO≥-13DB,RX≥-95DBM)/total number of samples x100%. Therefore, the CDMA (EC/IO≥-13DB,RX≥-95DBM) condition can be matched with the GSM (RX≥-95DBM) condition, and the two networks are evaluated as the unified evaluation criterion.

Speech quality Assessment

In the aspect of voice quality, GSM and CDMA voice coding methods and evaluation factors are different, CDMA use fer,gsm use BER, conventional road test evaluation can not be unified standard. Using the common MOS measurement standard of communication system, we can unify the two from the angle of voice quality feeling.

The commonly used methods of MOS evaluation include subjective MOS classification and objective MOS evaluation. The subjective MOS division adopts the itu-tp.800 and p.830 proposals, and the subjective sense contrast between the original corpus and the material which has been processed by the system is obtained by different people respectively, and then the MOS score and the average value are gained. Objective MOS evaluation adopts the Pesq method provided by itu-tp.862 proposal, which is tested by special instrument (such as Agilent VQT tester) or software.

Network Jamming Assessment

The evaluation method of wireless network jamming generally combines the distribution of network layout and repeater, terrain and ground features, and evaluates the interference in the net and the possible interference in the net by means of the actual road survey/data analysis and field investigation.

For the GSM system, this interference will affect the quality of the call, the emergence of broken words, words and other phenomena, mainly divided into network interference and external interference two types. Interference in the net refers to the area coverage or frequency planning defects, for the unreasonable honeycomb structure can be compensated by the frequency plan, for the network interference can be through frequency planning or clearing frequency method to solve.

The CDMA system is extremely sensitive to the disturbance, the network interference causes the honeycomb structure rationality to be mentioned the primary position, but the net outside interference needs the clear frequency, this point obviously is not as flexible as GSM.

Because the signal interference will directly affect the quality of the call, can easily be found directly from the road test, it is suggested that the following evaluation criteria should be considered in the road survey: GSM in the higher the receiving level (≥-80DBM) of all the road survey data, voice quality Qos=1 data accounted for the percentage of all data; CDMA in ec/ The total number of speech quality fer≤5% data is the percentage of all data in the IO≥-8DBM and RX≥-80DBM all the road survey data.

Network Layout evaluation

The evaluation of network layout includes: Integrated network scale, coverage area type, feature/terrain distribution, service zone design index, network structure, site/traffic burden density, indoor coverage strategy, etc. At this point, GSM and CDMA are the same, all require the network construction according to the strict honeycomb structure.

When evaluating a network layout, you can do this from the following three areas:

Whether the site topology conforms to the cellular structure. First, according to the Terrain Division area, each region with a base station as the center, calculated the surrounding 6 base station and center distance, so as to get average station spacing and average cell coverage radius l, and then with L as the benchmark, draw the standard honeycomb structure. The adjacent base station deviates from the standard honeycomb over 1/4 of the cell radius, then the statistic layout is unreasonable, and then the whole region and the whole network are evaluated.

The main cover layer antenna hanging high. If the antenna of a base station is below or above the average of 15%, the layout of the main cover antenna is unreasonable.

The proportion of super free community and super busy community. Select Busy when the language, when a base station statistics a super busy or super free community, then record. The ratio between the two nets is high, the layout is unreasonable.

Summing up the above statistics, we can evaluate the advantages and disadvantages of the layout of the two nets.

Resource Utilization Assessment

According to the front/back traffic volume of the network planning design and the front/reverse traffic volume can not objectively evaluate the GSM, CDMA network, and resource utilization can be well evaluated, it can reflect the actual network operation resources and planning and design of the overall proportion of resources, so as to effectively improve the utilization of resources , so that the operation of the network's investment costs to achieve the largest "cost-effective."

The specific evaluation process is as follows: from the network planning and design scheme to obtain the network scale, through the query results can get the actual busy time before/reverse traffic, the capacity of the Erl division, you can get the utilization of network resources, thus reflecting the network design load capacity.

Comparison of the speech and test indices

The speech index and test index are the important indexes to reflect the performance of wireless network, and the following two kinds of services are compared.

Evaluation of voice services. Can be compared by testing, it can also be compared through the analysis of the speech, the CDMA, GSM Test evaluation index includes the access failure rate, drop rate, switching success rate, position update success rate, voice intermittent ratio, unilateral call rate, echo and background noise rate, crosstalk rate and access time and so on.

GSM and CDMA networks have a consistent definition of these indicators and can be evaluated by field road measurements. In addition, the CDMA and GSM evaluation indicators include a number of important indicators of wireless networks, for these definitions, GSM and CDMA are basically the same, so you can use the data of the two networks for lateral evaluation.

First of all, you can determine whether the parameters of the two systems are up to par, if unqualified, then the problem of network is still very large; If the index is qualified, then the horizontal comparison of the two network indicators, a certain index is good to add a point, the final score high network quality good. Since the speech system can reflect the overall performance of the wireless network, it is better to use the speech Index to compare with the condition permitting.

Evaluation of data Services. The data Service network based on GSM is the 1X of GPRS,CDMA Data Service network. Among them, the CDMA1X data business language standards are still in development, so it is recommended to use test indicators for evaluation, concrete can be through ping, HTTP and FTP projects to achieve. By analyzing the indexes of CDMA1X and GPRS data service, it can be concluded that many evaluation standards of CDMA1X and GPRS are consistent, and it is not very difficult to achieve uniform standards in data transmission and time delay. The specific evaluation methods are suggested as follows: Two networks for the DT test, horizontal comparison of the two network indicators, a certain index is good to add a point, the final score high network quality.

To sum up, on the one hand, GSM and CDMA networks have similarities in many aspects, and can adopt unified evaluation standard. On the other hand, GSM and CDMA two kinds of mobile communication systems have certain commonness, it is feasible to evaluate them, but due to the difference of communication system, especially the change of air interface, To make the evaluation content and judgment of the two networks need to have a uniform guideline.