Data speed is cannot reach to upper limit

Today after checked the network for voices and data communication, i find new problem in the network, theoritically CDMA network can give 2 user with 153.6 kbps [5X system, using 16 code of walshcode] 2 users with 76,8 kbps [4X system, using 8 walshcode codeing] and 2 user with 38.4 kbps [3X system, using 4 Walshcode coding] or 4 users with 19.2 kbps [2x system using 2 walshcode code]data speed.
User can reach 153,6 kbps if user is very closed to BTS and get better Ec/Io, and low user active in that BTS sector, after tested and investigate our network with data call i just get 38.4 Kbps, its mean the reservation Supplemental Channel just give 3X system, its will be a problem for data network, after checked statistic data at that hour, i find just 2 active voice call and 1 active data call in the network.
ouch some new problem and i need some time to analyze this problem...
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