- Radio resource management
Radio resource management (RRM) is the system level control of
co-channel interferenceand other radio transmission characteristics in wireless communicationsystems, for example cellular networks, wireless networks and broadcastingsystems. RRM involves strategies and algorithms for controlling parameters such as transmit power, channel allocation, handover criteria, modulation scheme, error coding scheme, etc. The objective is to utilize the limited radio spectrum resources and radio network infrastructure as efficiently as possible.
RRM concerns multi-user and multi-cell network capacity issues, rather than point-to-point
channel capacity. Traditional telecommunications research and education often dwell upon channel codingand source codingwith a single user in mind, although it may not be possible to achieve the maximum channel capacity when several users and adjacent base stations share the same frequency channel. Efficient dynamic RRM schemes may increase the system capacity in an order of magnitude, which often is considerably more than what is possible by introducing advanced channel coding and source coding schemes. RRM is especially important in systems limited by co-channel interference rather than by noise, for example cellular systems and broadcast networks homogeneously covering large areas, and wireless networks consisting of many adjacent access points that may reuse the same channel frequencies.
The cost for deploying a wireless network is normally dominated by base station sites (real estate costs, planning, maintenance, distribution network, energy, etc) and sometimes also by frequency license fees. The objective of radio resource management is therefore typically to maximize the
system spectral efficiencyin "bit/s/Hz/base station site" or "Erlang/MHz/site", under constraint that the grade of serviceshould be above a certain level. The latter involves covering a certain area and avoiding outagedue to co-channel interference, noise, attenuation caused by long distances, fadingcaused by shadowing and multipath, Doppler shiftand other forms of distortion. The grade of service is also affected by blocking due to admission control, scheduling starvationor inability to guarantee quality of servicethat is requested by the users.
Static radio resource management
Static RRM involves manual as well as computer aided fixed
cell planningor radio network planning. Examples:
Frequency allocation band plans decided by standardization bodies, by national frequency authorities and in frequency resource auctions.
* Deployment of base station sites (or broadcasting transmitter site)
* Antenna heights
* Channel frequency plans
* Sector antenna directions
* Selection of
modulationand channel codingparameters
* Base station antenna
space diversity, for example
micro diversityusing antenna combining
macro diversitysuch as OFDM single frequency networks(SFN)
Static RRM schemes are used in many traditional wireless systems, for example
1Gand 2Gcellular systems, in today's wireless local area networks and in non-cellular systems, for example broadcasting systems. Examples of static RRM schemes are:
* Circuit mode communication using
Fixed channel allocation(FCA)
* Static handover criteria
Dynamic radio resource management
Dynamic RRM schemes adaptively adjust the radio network parameters to the traffic load, user positions, quality of service requirements, etc. Dynamic RRM schemes are considered in the design of wireless systems, in view to minimize expensive manual cell planning and achieve "tighter"
frequency reusepatterns, resulting in improved system spectral efficiency.
Some schemes are centralized, where several base stations and access points are controlled by a
Radio Network Controller(RNC). Others are distributed, either autonomous algorithms in mobile stations, base stations or wireless access points, or coordinated by exchanging information among these stations.
Examples of dynamic RRM schemes are:
Dynamic Channel Allocation(DCA) or Dynamic Frequency Selection(DFS) algorithms
* Traffic adaptive
handovercriteria, allowing "cell breathing"
Single antenna interference cancellation(SAIC)
diversity schemes, for example
Dynamic Single Frequency Networks(DSFN)
Phased array antennawith
Multiple-input multiple-output communications(MIMO)
Dynamic bandwidth allocationusing resource reservation multiple accessschemes or statistical multiplexing, for example Spread spectrumand/or packet radio
Channel-dependent scheduling, for instance
Max-min fair schedulingusing for example fair queuing
Proportionally fair schedulingusing for example weighted fair queuing
Maximum throughput scheduling(gives low grade of servicedue to starvation)
Dynamic packet assignment(DPA)
Packet and Resource Plan Scheduling(PARPS) schemes
Mobile ad-hoc networks using multihopcommunication
Electromagnetic interference control
IEEE 802.11h- Transmit power controland dynamic frequency selection(DFS) for wireless local area networks
IEEE 802.11k- RRM for wireless local area networks
Multiple access methods
Radio Network Controller(RNC)
* J. Zander, S-L Kim, M. Almgren (2001), Radio Resource Management for Wireless Networks, Artech House Publishers, ISBN:1580531466.
* N. D. Tripathi, J. H. Reed, H. F. Vanlandingham (2001), Radio Resource Management in Cellular Systems, Springer, ISBN:079237374X [http://books.google.com/books?id=xex6Z-DquTwC&dq=radio+resource+management]
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