Radio resource management

Last updated

Radio resource management (RRM) is the system level management of co-channel interference, radio resources, and other radio transmission characteristics in wireless communication systems, for example cellular networks, wireless local area networks, wireless sensor systems, and radio broadcasting networks. [1] [2] RRM involves strategies and algorithms for controlling parameters such as transmit power, user allocation, beamforming, data rates, handover criteria, modulation scheme, error coding scheme, etc. The objective is to utilize the limited radio-frequency spectrum resources and radio network infrastructure as efficiently as possible.

Contents

RRM concerns multi-user and multi-cell network capacity issues, rather than the point-to-point channel capacity. Traditional telecommunications research and education often dwell on channel coding and source coding with a single user in mind, but when several users and adjacent base stations share the same frequency channel it may not be possible to achieve the maximum channel capacity. Efficient dynamic RRM schemes may increase the system spectral efficiency by 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. So, the objective of radio resource management is typically to maximize the system spectral efficiency in bit/s/Hz/area unit or Erlang/MHz/site, under some kind of user fairness constraint, for example, that the grade of service should be above a certain level. The latter involves covering a certain area and avoiding outage due to co-channel interference, noise, attenuation caused by path losses, fading caused by shadowing and multipath, Doppler shift and other forms of distortion. The grade of service is also affected by blocking due to admission control, scheduling starvation or inability to guarantee quality of service that is requested by the users.

While classical radio resource managements primarily considered the allocation of time and frequency resources (with fixed spatial reuse patterns), recent multi-user MIMO techniques enables adaptive resource management also in the spatial domain. [3] In cellular networks, this means that the fractional frequency reuse in the GSM standard has been replaced by a universal frequency reuse in LTE standard.

Static radio resource management

Static RRM involves manual as well as computer-aided fixed cell planning or radio network planning. Examples:

Static RRM schemes are used in many traditional wireless systems, for example 1G and 2G cellular systems, in today's wireless local area networks and in non-cellular systems, for example broadcasting systems. Examples of static RRM schemes are:

Dynamic radio resource management

Dynamic RRM schemes adaptively adjust the radio network parameters to the traffic load, user positions, user mobility, quality of service requirements, base station density, etc. Dynamic RRM schemes are considered in the design of wireless systems, in view to minimize expensive manual cell planning and achieve "tighter" frequency reuse patterns, 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. [1]

Examples of dynamic RRM schemes are:

Inter-cell radio resource management

Future networks like the LTE standard (defined by 3GPP) are designed for a frequency reuse of one. In such networks, neighboring cells use the same frequency spectrum. Such standards exploit Space Division Multiple Access (SDMA) and can thus be highly efficient in terms of spectrum, but required close coordination between cells to avoid excessive inter-cell interference. Like in most cellular system deployments, the overall system spectral efficiency is not range limited or noise limited, but interference limited. [1] Inter-cell radio resource management coordinates resource allocation between different cell sites by using multi-user MIMO techniques. There are various means of inter-cell interference coordination (ICIC) already defined in the standard. [4] Dynamic single-frequency networks, coordinated scheduling, multi-site MIMO or joint multi-cell precoding are other examples for inter-cell radio resource management. [3] [5]

See also

Related Research Articles

Time-division multiple access

Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream.

In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode.

Space-division multiple access (SDMA) is a channel access method based on creating parallel spatial pipes using advanced antenna technology next to higher capacity pipes through spatial multiplexing and/or diversity, by which it is able to offer superior performance in radio multiple access communication systems. In traditional mobile cellular network systems, the base station has no information on the position of the mobile units within the cell and radiates the signal in all directions within the cell in order to provide radio coverage. This method results in wasting power on transmissions when there are no mobile units to reach, in addition to causing interference for adjacent cells using the same frequency, so called co-channel cells. Likewise, in reception, the antenna receives signals coming from all directions including noise and interference signals. By using smart antenna technology and differing spatial locations of mobile units within the cell, space-division multiple access techniques offer attractive performance enhancements. The radiation pattern of the base station, both in transmission and reception, is adapted to each user to obtain highest gain in the direction of that user. This is often done using phased array techniques.

Cellular network Communication network

A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver. These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell.

A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best wireless channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels in wireless spectrum, then accordingly changes its transmission or reception parameters to allow more concurrent wireless communications in a given spectrum band at one location. This process is a form of dynamic spectrum management.

This article discusses the mobile cellular network aspect of teletraffic measurements. Mobile radio networks have traffic issues that do not arise in connection with the fixed line PSTN. Important aspects of cellular traffic include: quality of service targets, traffic capacity and cell size, spectral efficiency and sectorization, traffic capacity versus coverage, and channel holding time analysis.

Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, and sometimes by the medium access control.

Orthogonal frequency-division multiple access Multi-user version of OFDM digital modulation

Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users. This allows simultaneous low-data-rate transmission from several users. Channel hardening: channel hardening means that the fading channels behaves as if it was a non fading channel. The randomness is still there but its impact on the communication is still negligible.

E-UTRA

E-UTRA is the air interface of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) upgrade path for mobile networks. It is an acronym for Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access, also referred to as the 3GPP work item on the Long Term Evolution (LTE) also known as the Evolved Universal Terrestrial Radio Access (E-UTRA) in early drafts of the 3GPP LTE specification. E-UTRAN is the initialism of Evolved UMTS Terrestrial Radio Access Network and is the combination of E-UTRA, user equipment (UE), and E-UTRAN Node B or Evolved Node B (eNodeB).

Maximum throughput scheduling is a procedure for scheduling data packets in a packet-switched best-effort communications network, typically a wireless network, in view to maximize the total throughput of the network, or the system spectral efficiency in a wireless network. This is achieved by giving scheduling priority to the least "expensive" data flows in terms of consumed network resources per transferred amount of information.

In the field of wireless communication, macrodiversity is a kind of space diversity scheme using several receiver antennas and/or transmitter antennas for transferring the same signal. The distance between the transmitters is much longer than the wavelength, as opposed to microdiversity where the distance is in the order of or shorter than the wavelength.

Dynamic Single Frequency Networks (DSFN) is a transmitter macrodiversity technique for OFDM based cellular networks.

In radio resource management for wireless and cellular networks, channel allocation schemes allocate bandwidth and communication channels to base stations, access points and terminal equipment. The objective is to achieve maximum system spectral efficiency in bit/s/Hz/site by means of frequency reuse, but still assure a certain grade of service by avoiding co-channel interference and adjacent channel interference among nearby cells or networks that share the bandwidth.

Multi-user MIMO (MU-MIMO) is a set of multiple-input and multiple-output (MIMO) technologies for multipath wireless communication, in which multiple users or terminals, each radioing over one or more antennas, communicate with one another. In contrast, single-user MIMO (SU-MIMO) involves a single multi-antenna-equipped user or terminal communicating with precisely one other similarly equipped node. Analogous to how OFDMA adds multiple-access capability to OFDM in the cellular-communications realm, MU-MIMO adds multiple-user capability to MIMO in the wireless realm.

In radio, cooperative multiple-input multiple-output is a technology that can effectively exploit the spatial domain of mobile fading channels to bring significant performance improvements to wireless communication systems. It is also called network MIMO, distributed MIMO, virtual MIMO, and virtual antenna arrays.

MIMO Use of multiple antennas in radio

In radio, multiple-input and multiple-output, or MIMO, is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi), IEEE 802.11ac (Wi-Fi), HSPA+ (3G), WiMAX, and Long Term Evolution (LTE). More recently, MIMO has been applied to power-line communication for three-wire installations as part of the ITU G.hn standard and of the HomePlug AV2 specification.

CDMA spectral efficiency refers to the system spectral efficiency in bit/s/Hz/site or Erlang/MHz/site that can be achieved in a certain CDMA based wireless communication system. CDMA techniques are characterized by a very low link spectral efficiency in (bit/s)/Hz as compared to non-spread spectrum systems, but a comparable system spectral efficiency.

C-RAN (Cloud-RAN), sometimes referred to as Centralized-RAN, is an architecture for cellular networks. 9 years after it was disclosed in patent applications filed by U.S. companies. Simply speaking, C-RAN is a centralized, cloud computing-based architecture for radio access networks that supports 2G, 3G, 4G and future wireless communication standards. Its name comes from the four 'C's in the main characteristics of C-RAN system, "Clean, Centralized processing, Collaborative radio, and a real-time Cloud Radio Access Network".

The first smart antennas were developed for military communications and intelligence gathering. The growth of cellular telephone in the 1980s attracted interest in commercial applications. The upgrade to digital radio technology in the mobile phone, indoor wireless network, and satellite broadcasting industries created new opportunities for smart antennas in the 1990s, culminating in the development of the MIMO technology used in 4G wireless networks.

Multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) is the dominant air interface for 4G and 5G broadband wireless communications. It combines multiple-input, multiple-output (MIMO) technology, which multiplies capacity by transmitting different signals over multiple antennas, and orthogonal frequency-division multiplexing (OFDM), which divides a radio channel into a large number of closely spaced subchannels to provide more reliable communications at high speeds. Research conducted during the mid-1990s showed that while MIMO can be used with other popular air interfaces such as time-division multiple access (TDMA) and code-division multiple access (CDMA), the combination of MIMO and OFDM is most practical at higher data rates.

References

  1. 1 2 3 Miao, Guowang; Zander, Jens; Sung, Ki Won; Slimane, Ben (2016). Fundamentals of Mobile Data Networks. Cambridge University Press. ISBN   978-1107143210.
  2. ↑ Tripathi, N. D.; Reed, J. H.; Vanlandingham, H. F. (2001). Radio Resource Management in Cellular Systems. Springer. ISBN   079237374X.
  3. 1 2 Björnson, E.; Jorswieck, E. (2013). "Optimal Resource Allocation in Coordinated Multi-Cell Systems". Foundations and Trends in Communications and Information Theory. 9 (2–3): 113–381. doi:10.1561/0100000069.
  4. ↑ Pauli, V.; Naranjo, J. D.; Seidel, E. (December 2010). "Heterogeneous LTE Networks and Inter-Cell Interference Coordination". White Paper, Nomor Research.
  5. ↑ Gesbert, D.; Hanly, S.; Huang, H.; Shamai, S.; Simeone, O.; Yu, W. (December 2010). "Multi-cell MIMO cooperative networks: A new look at interference". IEEE Journal on Selected Areas in Communications. 28 (9): 1380–1408. doi:10.1109/JSAC.2010.101202. S2CID   706371.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.