MQAM/CDMA for increased cellular capacity

The CDMA (code division multiple access) technique can provide efficient multiple access to a large number of users. CDMA as a multiple access method can be combined with any desired modulation technique. The author considers the result of combining CDMA access with a high-efficiency modulation technique, e.g., 256-QAM (quadrature amplitude modulation), and whether the bandwidth efficiency of high-level QAM can be used to overcome the bandwidth inefficiency of CDMA. A mathematical model is built to compare cellular capacity obtained with and without MQAM-CDMA use. It is seen that MQAM-CDMA leads to reduced capacity, indicating that the advantages of the two schemes are not enough to overcome each other's disadvantages.