Software Radio refers to a tendency to increase the proportion of software component in the realization of a communication system. This approach brings some advantages like decrease in the implementation cost, ease of modification and upgrading, and facilities to support multiple standards in a single system. Researchers in this field focus on topics such as development of hardware tools, production of multi-purpose development kits, introducing new software algorithms and implementation techniques, proposing standard communication protocols oriented softwares and realization of the Cognitive radio concept. Software Radio, as a general field, exploits the developments in digital communication and electronics fileds. A Wireless Local Loop, or briefly WLL, is a communication network that provides wireless communications between internal users, and the ability of bidirectional contacts between internal and external users. A WLL, as a general communication network, may be based upon various protocols in its infrastructure. GSM standards, have a world-wide popularity and GSM compliant user terminals are easily available almost anywhere. Then, these standards provide an appropriate protocol collection to setup a WLL. However some challenges like security and coexistence with licensed operators should be considered. In this research, a general hardware is used to receive and transfer radio signals. The received signals are sampled and digitized by hardware, and the resultatnt digital symbols are transfered to a personal computer, through a USB2 connector, for processing. The software is designed on Linux operating system and performs all the processes, from physical layer to the highest control layer. This software comprises a transceiver, a GSM stack and a control layer. The functions such as demodulation, decoding, processing of triple layers of Air interface, and predefined transactions of GSM networks are included in the software in the receive path. Equivalent functions are designed for reverse path too. In a real GSM network, these functions and predefined procedures like Mobile Originating Call (MOC), Mobile Terminating Call (MTC), Short Message Service-Mobile Originated (SM-MO) and Short Message Service -Mobile Terminated (SM-MT), are distributed among several parts like Base Transceiver Station (BTS), Base Station Controller (BSC), Mobile Switching Center (MSC) and Short Message Service Center (SMSC). The designed software realizes needed functions completely, in contact with a Back to Back User Agent (B2BUA), and uses some VoIP protocols. The implemented wireless local loop in this work, uses a GSM-VoIP infrastructure to provide stable calls between internal mobile stations. Internal users can communicate to external users ... Keywords: Software Radio, GSM, VoIP, Wireless Local Loop