In PMP system: how can I improve uplink rates to 4Mbps?



In PMP system, when I test throuputs AP-SM,I found however I adjust downlink percent, for example :10%,20%,or 30%,the uplink rates is also low,only less 2 Mbps.


But in PTP system,when I set a downlink percent 25%, BH-BH test is : downlink rate is 1.8 Mbps,and uplink rate is 5.4Mbps.


Can somebody tell me the reason? Thank u very much.