MAC-CR.ppt

[Virtual Presenter] Today I am going to discuss a solution to the challenge of effectively managing the access to the scarce radio spectrum resources: Channel Aware Medium Access Control in Cognitive Radio Networks..

[Audio] We will be discussing channel aware medium access control in cognitive radio networks. Cognitive radios are a technology that address the challenge of spectrum being a limited resource. With the rising demand for communication services, radio spectrum is becoming ever scarcer. Solutions that make more effective use of the limited spectrum are needed, and cognitive radios present a unique way of doing so. It has also been demonstrated that using cognitive radios can enhance spectral usage in urban areas. Let us now delve further into this topic..

[Audio] Cognitive Radio Networks require a Channel Aware Medium Access Control (MAC) in order to allow unlicensed users to access vacant radio spectrum to transmit and receive data. This is done by identifying frequency bands that are either occupied by licensed users or those that are vacant, also referred to as "spectrum holes". Medium access for unlicensed users in cognitive networks needs to be highly dynamic and opportunistic..

[Audio] We will be discussing Channel Aware Medium Access Control in Cognitive Radio Networks. Cognitive Radio is a form of wireless communication in which the devices can sense the environment and adapt their operating parameters to allow for more efficient use of the available spectrum. This has attracted the attention of the research community who are focusing on designing robust and effective spectrum access techniques. It is closely related to the development of MAC protocols in multichannel wireless networks, but requires different design considerations than multichannel wireless networks. The development of CR-MAC protocols has often borrowed ideas from existing protocols in multichannel wireless networks, providing the foundation for development and research..

[Audio] Cognitive radio networks have potential to improve channel access control by employing a range of techniques and protocols such as channel sensing, detection of primary users, dynamic channel selection and robust channel switching. A better understanding of how these networks work can be obtained by exploring these techniques and how they enable the maximization of usage of both licensed and unlicensed bands..

[Audio] Today, I will talk about Channel Aware Medium Access Control in Cognitive Radio Networks. Specifically, I want to discuss the IEEE 802.22 WRAN standard, which is aimed at using Cognitive Radio techniques to allow shared access of unused spectrum allocated to television broadcast services. In a WRAN network, white spaces in television broadcasts are used to provide broadband access. The goal of WRAN is to give Internet access to areas that are not easily accessible. It should be noted that the IEEE 802.22 WRAN standard is centralized, and doesn't serve a distributed architecture. Currently, there is no similar standard for medium access in distributed network cases..

[Audio] Today, we will be discussing the concept of channel aware medium access control in cognitive radio networks. Most of the schemes used to control the information exchange in design of distributed MACs require an overhead that is considerably higher than in simple wireless networks. This overhead is most commonly achieved through out of band signaling or the use of a dedicated control channel. Additionally, an IEEE 802.11 DCF like architecture has also proven to be very popular..

[Audio] Today we will be talking about Channel Aware Medium Access Control in Cognitive Radio Networks. As you can see in this slide, various CR - MAC protocols - or in other words, protocols that help with the management and access control - have been proposed in literature. These protocols vary in their complexity, structure, size, and more, which means they are well-suited for different applications. For this reason, we must be aware of all of these protocols, and their respective benefits and limitations..

[Audio] Today I will talk about Channel Aware Medium Access Control in Cognitive Radio Networks. Channel Aware MAC schemes focus on exploiting the channel state information around a user, making a user self aware of its surroundings and enabling it to make independent decisions. By using this approach, competition can be made fair and thus, throughput values comparable to centralized scheduling schemes can be achieved. Some example works in this field are CAD-MAC and CAAC..

[Audio] We will be learning about Channel Aware Medium Access Control (CAD-MAC) in Cognitive Radio Networks. CAD-MAC is a distributed MAC protocol intended for competitive networks, where users attempt communication over a single channel. It is a channel-aware adaptation of Aloha, where each user opportunistically contends for its success. This protocol utilizes direct cues from the channel conditions, allowing it to select the best links in terms of channel states and potentially achieving performance close to that of centralized schedulers..

[Audio] Channel Aware Medium Access Control in Cognitive Radio Networks is a type of network which consists of three step signaling before confirming the successful establishment of a link. Every user in the network also maintains and modifies its own personal threshold values extracted from Channel State Information. In addition, channels are modelled as Rayleigh fading and approximately 10 percent of the frame time is spent on sorting out the contending links. This type of network will optimize the network throughput while decreasing the interference between the selected links..

[Audio] We are going to discuss an example of a medium access technique, namely channel aware medium access control, or CAD-MAC, for cognitive radio networks. This technique is based on the concept of the time frame, with time frames being organized in a way to allow for more efficient resource sharing. This involves reserving certain channels for exclusive use and performing spectrum sensing to determine which channels are available for use. Let's take a closer look at the details..

[Audio] User i sends a request to user j in Step 1 of the signaling exchange in the context of "Channel Aware Medium Access Control in Cognitive Radio Networks". Step 2 involves user j broadcasting either an idle or busy signal, and Step 3 involves user i broadcasting an occupied signal. Upon completion of the exchange, user i remains active and the threshold H is adjusted. Depending upon the steps taken, the outcome can be either success or fail..

[Audio] Discussing Channel Aware Medium Access Control (CAMAC) in Cognitive Radio Networks is necessary. CAMAC is a protocol which optimizes the thresholds for transmissions to minimize collisions. When a collision has taken place, the threshold for the next resolution slot is increased. If there were no requests transmitted in the last resolution slot, the receiver can invite requests by decreasing the thresholds, otherwise it remains the same..

[Audio] In a Cognitive Radio Network (CRN), environment adaptivity is enabled through the optimization of thresholds. If there is a collision of requests, the thresholds can be increased. If there was no request transmitted in the previous resolution slot, then the thresholds can be decreased. If none of these two cases apply, then the thresholds can remain the same..

[Audio] Discussing Channel Aware Medium Access Control in Cognitive Radio Networks, we will be examining spectrum mobility, dynamic spectrum access and a channel switching mechanism in multichannel distributed networks. Additionally, we will be exploring our proposal which uses a separate control channel and time synchronization of secondary users. Examining our design, it was simulated over several test topologies with the presence of both primary and secondary users..

[Audio] Taking a look at Channel Aware Medium Access Control in Cognitive Radio Networks, changes will be made to the control signaling mechanism. Different ways of selecting best possible links for contentions by considering all opportunities that are available to users across the spectrum will be explored. The switching mechanism will also be considered to see how failing to get success for data transmission on one channel can make a user contend for another channel. Threshold modification and how to consider the dynamic spectral environment in calculating and optimizing these values will be discussed..

[Audio] Discussions will focus on Channel Aware Medium Access Control in Cognitive Radio Networks. We will examine the presence of both primary and secondary users and how they can be managed to optimize utilization of available spectrum..

[Audio] We will be talking about Channel Aware Medium Access Control in Cognitive Radio Networks. This type of medium access control concentrates on amending the control signaling interchange, so that nodes can rapidly spot the channel and adjust to the surroundings suitably. This permits nodes to make the most of the present resources in a variable way, particularly in a continually changing climate. Therefore, let's discover how this functions!.

[Audio] We'll be discussing Channel Aware Medium Access Control in Cognitive Radio Networks. There are two types of Channel Aware Medium Access Control - Multichannel CAD-MAC and Single Channel CAD-MAC - which are both used in Cognitive Radio Networks when dealing with randomly distributed users. This concludes the presentation, hoping it was informative..

[Audio] We have been discussing channel aware medium access control in cognitive radio networks. Applying a slotted aloha protocol for contention among users with varying spectral opportunities has produced good values of network throughput for secondary users. Our design is able to fairly choose interference free links among the contending users, making it highly probable the selection of those links with comparably better channel states in a neighborhood. Our protocol can be implemented for network cases with both primary and secondary users present. Thank you for your attention to this discussion..