**5. Open issues in POCA design**

In spite of a reasonable amount of research in the late literature, there are still some challenges and open issues that need to be addressed in designing efficient channel assignment schemes exploiting POCs, particularly in WMNs. Below, we outline what we believe some of these challenges and open issues are.

## **5.1. Capturing self interference**

As explained in Section 2.2, self-interference restricts parallel communication originating from a node having more than one radio unless these radios operate on completely orthogonal channels (OCs). Since, there are only three OCs for IEEE 802.11b/g in the 2.4GHz band, there is a need to further investigate how the self-interference issue can be better addressed. Few CA schemes have addressed self-interference in multi radio MWNs and we believe that there is room for improvement.

### **5.2. Modeling interference of POCs**

More robust and efficient modeling schemes are required to intelligently capture the interference experienced by neighboring nodes operating on POCs in MRMC-WMNs. Although existing approaches do partially capture one or two types of interferences in a WMN, they are not complete solutions (they do not capture all the different types of interferences realistically). Furthermore issues arising from geographical positions of neighboring nodes and the availability of variable data rates still pose major challenges for POCA algorithms.

### **5.3. Lack of simulation tools**

Most existing simulators [29-31] still do not support underlying physical models and easy POC evaluation scripting to capture partial interference between adjacent nodes in WMNs. However, we believe the reason for the lack of this feature is because the concept of POCs in CA schemes is relatively new and is still progressing and evolving to its maturity.
