CC3200: How to increase the PHY RATE in 'http_client_demo'

Dear Sir,

I'm using  the 'http_client_demo' of CC3200, we want to send files on http, when CC3200 is close to AP, the transfer is ok, but when it becomes further, the transfer  mostly failed. so we want to increase the phy_rate, or the tx_power, but how should i set ?  the followings are the steps of my demo, it mostly faied at the RED part.

1）sl_Start(NULL,NULL,NULL);//

2）WlanConnect –〉sl_WlanPolicySet，sl_WlanConnect

3）ret = HTTP_ConnectToServer(g_HttpHandle, g_HTTP_Server);

   HTTPCli_setRequestFields(g_HttpHandle, fields);

HTTPCli_setRequestFields(g_HttpHandle, fields);

HTTPCli_sendRequest(g_HttpHandle, HTTPCli_METHOD_POST,HTTP_SERVER_POST_REQUEST_URI, 0);

HTTPCli_sendRequestBody(g_HttpHandle, (const char*)g_data_upload_via_http_buffer, databegin_len);

HTTP_ReadResponse(g_HttpHandle);

HTTP_DisconnectFromServer(g_HttpHandle);