Fulfilling the Rate Demands: Subcarrier-Based Shared Resource Allocation

Fulfilling the Rate Demands: Subcarrier-Based Shared Resource Allocation

Ravikant Saini (Indian Institute of Technology Delhi, India) and Swades De (Indian Institute of Technology Delhi, India)
DOI: 10.4018/978-1-5225-2023-8.ch003
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Mobile connectivity these days is no more a privilege but a basic necessity. This has led to exponentially-increasing data rate demands over the network, causing tremendous pressure to the access network service planners. Orthogonal frequency division multiple access (OFDMA) is being considered for resource allocation in higher generation communication networks, where spectrum efficiency improvement while fulfilling the users' data rate demands is a key aspect of interest. Normally resource allocation is considered from the viewpoint of users, with the users selecting their best available subcarriers. In this chapter, the resource allocation problem is approached from the subcarrier's perspective. Besides the conventional user-based scheme, a recent subcarrier-based shared resource allocation scheme is presented that selects the best user(s) for each subcarrier and assigns the subcarrier either to a single user or more than one user on time-shared basis according to their current SNRs. Unlike the user-based schemes, in the proposed scheme each user can contend for any subcarrier.
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With the increasing overlap of users’ active mobile time and their awake time, mobile connectivity is expected to be always present anytime, anywhere. Users find it hard to wait for any time lag in connection setup due to the requirement of remaining connected on social applications, be it early morning or just before they are off to bed. Thus, mobile connectivity these days is no more a desire, but it is appearing as a basic need of the user. But the requirement of instant connectivity raises immense pressure on the wireless infrastructure planners, as this is the last-mile which is the bottleneck. The flexibility of access network has taken a great leap following the transition from wired (e.g., dial-up connection, Digital Subscriber Line (DSL)) to broadband wireless (e.g., Long-Term Evolution – Advanced (LTE-A), Worldwide Interoperability for Microwave Access (WiMAX)) for the last-mile connectivity. Yet, the current generations of wireless access network protocols find it hard to cater to the ever-increasing data rate demands of the mobile users. These days, a mobile devices is no longer a calling facility but a data hungry demon with a day-by-day increasing appetite. With the social networking platforms, such as, Facebook and YouTube, as common information sharing avenues, and powerful smart phones in every pocket, it is quite formidable to satisfy a user with anything less than the prefect quality video on the move. One strong physical layer technology is required to cater to the data rate demands of mobile users and stand hard against the impairments of wireless channel. Orthogonal frequency division multiple access (OFDMA) which divides a wide band channel into multiple narrow band channels, appears as a robust technology against the multipath fading effect of wireless channel. Next section provides a brief overview of resource allocation schemes in OFDMA.

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