Background:

With recent proliferation in wireless services and amplification in number of end-users, wireless industry is fast moving toward a new wireless networking model where wireless service providers are finding it difficult to satisfy users and increase revenue with just the spectrum statically allocated. Spectrum usage being both space and time dependent, a static allocation often leads to low spectrum utilization and “artificial scarcity of spectrum resulting in significant amount of “white space' (unused band) available in several spectral bands that could be exploited by both licensed and unlicensed services. For example, the extent of this white space was measured in New York City during the 2004 Republic National Convention. In order to break away from the inflexibility and inefficiencies of static spectrum allocation, the new concept of Dynamic Spectrum Access (DSA) is being investigated by network and radio engineers, policy makers, and economists.

Summary:

The present invention overcomes the limitations faced by static radio devices by providing methods and apparatus for dynamic spectrum access with the help of cognitive radios. Software driven cognitive radio functionality is implemented by focusing on the two most important regulatory aspects: sensing/detection of primary incumbents and dynamic channel switching upon detection of the primary incumbents. The design and implementation of the present invention can be successfully deployed on any off-the-shelf wireless access card. The Software abstraction hides the physical layer details from the upper layers in the modified network protocol stack as will be described hereinafter. With the programmable hardware abstraction layer, the cognitive radio can configure the transmission/reception parameters automatically to operate at any unused frequency in the allowable spectrum bands unlike the existing radios which can only be configured to operate statically at any one frequency channel. A goal of the cognitive radio system architecture and design is to operate on any unused spectrum band efficiently with high data throughput, conduct sensing/detection of primary incumbents to comply with the mandatory regulation that cognitive radio must not interfere the primary incumbents; achieve seamless spectrum band switching in dynamic spectrum access networks if primary incumbents are detected in the current operating band. This goal poses several challenges involved with switching to new channel upon sensing/detection of primary incumbents: When a wireless card switches to a new channel, the hardware is reset and the MAC will be restarted. However, this process can induce a delay of the order of 100 ms. This is a significant delay overhead for channel switching where the aim is to switch as fast as possible. Therefore, a modified implementation is needed to eliminate this overhead.

When a wireless radio or card switches (moves) to a new channel, it reconfigures the frequency channel. Thus, for the duration of switching, it needs to stop the data transmitted from the upper layers. This operation will adversely affect the performance at the higher layers. In order to solve this issue, an extra data buffer is needed to achieve seamless channel switching. Communicating cognitive radio transmitter-receiver nodes with dynamic channel switching capability must successfully synchronize with each other prior to the actual dynamic channel switching to move to a new channel and resume communication. Thus, proper synchronization between the communicating cognitive radio nodes is a key issue; otherwise the nodes may end up in different channels resulting in the loss of the communication link. The dynamic frequency switching policy must be simple with a goal towards fast switching, increased robustness, reduced overhead and increased effective throughput. Some of the challenges involved with sensing/detection of primary incumbents are listed below: Primary incumbents sensing/detection is one of the most important tasks for cognitive radio to comply with the mandatory regulatory aspect. However, the question is what would be an optimal strategy of sensing/detection. Energy and interference/noise detection can be one-way of understanding the presence of other communications; however, mere energy detection cannot distinguish between cognitive radio communications and primary incumbents’ communications. Moreover, energy detection is more applicable when the cognitive radios are quiet; however, a major drawback in making all the cognitive radio nodes quiet is that normal communication is lost for the sensing duration resulting in degraded performance.

Benefits:

- Effective spectrum utilization

- A device capable of accessing the spectrum dynamically

- Helps increase number of customers by maintaining the same spectrum allocation

Applications:

- Telecom operators

- Broadband operators

- Decrease in the need for high bandwidth satellites

Full Patent: Method And Apparatus For Dynamic Spectrum Access