In the field of wireless communication, ''macrodiversity''
[D. Gesbert, S. Hanly, H. Huang, S. Shamai, O. Simeone, W. Yu]
Multi-cell MIMO cooperative networks: A new look at interference
IEEE Journal on Selected Areas in Communications, vol. 28, no. 9, pp. 1380–1408, Dec. 2010.[D. A. Basnayaka, P. J. Smith and P. A. Martin]
Performance analysis of macrodiversity MIMO systems with MMSE and ZF receivers in flat Rayleigh fading
IEEE Transactions on Wireless Communications, vol. 12, no. 5, pp. 2240–2251, May 2013. is a kind of
space diversity
Antenna diversity, also known as space diversity or spatial diversity, is any one of several wireless diversity schemes that uses two or more antennas to improve the quality and reliability of a wireless link. Often, especially in urban and ind ...
scheme using several receiver or transmitter antennas for transferring the same signal. The distance between the transmitters is much longer than the
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
, as opposed to
microdiversity where the distance is in the order of or shorter than the wavelength.
In a
cellular 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 (typically thre ...
or a
wireless LAN
A wireless LAN (WLAN) is a wireless computer network
A wireless network is a computer network that uses wireless data connections between network nodes.
Wireless networking is a method by which homes, telecommunications networks and bus ...
, macro-diversity implies that the antennas are typically situated in different
base station
Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service."
The term is used in the context of mobile telephony, wireless com ...
sites or
access points. Receiver macro-diversity is a form of
antenna combining Diversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal.
Various techniques
Various diversity combining techniques can be distinguished:
* Equal-gain com ...
, and requires an infrastructure that mediates the signals from the local antennas or receivers to a central receiver or decoder. Transmitter macro-diversity may be a form of
simulcasting
Simulcast (a portmanteau of simultaneous broadcast) is the broadcasting of programmes/programs or events across more than one resolution, bitrate or medium, or more than one service on the same medium, at exactly the same time (that is, simultane ...
, where the same signal is sent from several nodes. If the signals are sent over the same physical channel (e.g. the channel frequency and the spreading sequence), the transmitters are said to form a
single-frequency network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.
Analog AM and FM radio broadcast networks as well as digital broadcast networks can operate ...
—a term used especially in the broadcasting world.
The aim is to combat
fading
In wireless communications, fading is variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. Fading is often modeled as a random process. A fading channel is a ...
and to increase the received signal strength and signal quality in exposed positions in between the base stations or access points. Macro diversity may also facilitate efficient
multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...
services, where the same frequency channel can be used for all transmitters sending the same information. The diversity scheme may be based on transmitter (downlink) macro-diversity and/or receiver (uplink) macro-diversity.
Examples
*
CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication ...
soft handoff Soft handover or soft handoff refers to a feature used by the CDMA and W-CDMA standards, where a cell phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the same physical cell site (a sec ...
:
**
UMTS
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the Inte ...
softer handoff Soft handover or soft handoff refers to a feature used by the CDMA and W-CDMA standards, where a cell phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the same physical cell site (a sec ...
.
*
OFDM
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital commun ...
and
frequency-domain equalization
Single-carrier FDMA (SC-FDMA) is a frequency-division multiple access scheme. It is also called linearly precoded OFDMA (LP-OFDMA). Like other multiple access schemes (TDMA, FDMA, CDMA, OFDMA), it deals with the assignment of multiple users to a ...
(FDE) based
single-frequency network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.
Analog AM and FM radio broadcast networks as well as digital broadcast networks can operate ...
s (SFN) are a form of ''transmitter macrodiversity'' used in broadcasting networks such as
DVB-T
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Febr ...
and
DAB
**
Dynamic single-frequency networks {{Unreferenced, date=January 2008
Dynamic Single Frequency Networks (DSFN) is a transmitter macrodiversity technique for OFDM based cellular networks.
DSFN is based on the idea of single frequency networks (SFN), which is a group of radio transmit ...
(DSFN), where a scheduling scheme adapts the SFN formations dynamically to traffic conditions and/or receiver conditions
**
802.16e
8 (eight) is the natural number following 7 and preceding 9.
In mathematics
8 is:
* a composite number, its proper divisors being , , and . It is twice 4 or four times 2.
* a power of two, being 2 (two cubed), and is the first number of t ...
macro diversity handover (MDHO)
** 3GPP
long-term evolution
In telecommunications, long-term evolution (LTE) is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA standards. It improves on those standards' capacity and speed by usi ...
(LTE) multicast-broadcast single-frequency network (MBSFN), making it possible to efficiently send the same data to many mobiles in adjacent cells.
**
Cooperative diversity Cooperative diversity is a cooperative multiple antenna technique for improving or maximising total network channel capacities for any given set of bandwidths which exploits user diversity by decoding the combined signal of the relayed signal and t ...
, for example 3GPP long term evolution (LTE) ''coordinated multipoint transmission/reception'' (CoMP), making it possible to increase the data rate to a mobile situated in the overlap of several base station transmission ranges.
Forms
The baseline form of macrodiversity is called single-user macrodiversity. In this form, single user which may have multiple antennas, communicates with several base stations. Therefore, depending on the spatial degree of freedom (DoF) of the system, user may transmit or receive multiple independent data streams to/from base stations in the same time and frequency resource.
* Single-user macrodiversity
** Uplink macrodiversity
** Downlink macrodiversity
In next more advanced form of macrodiversity, multiple distributed users communicate with multiple distributed base stations in the same time and frequency resource. This form of configuration has been shown to utilize available spatial DoF optimally and thus increasing the cellular system capacity and user capacity considerably.
* Multi-user macrodiversity
** Macrodiversity multiple access channel (MAC)
** Macrodiversity broadcast channel (BC)
[M. K. Karakayali, G. J. Foschini, and R. A. Valenzuela]
Network coordination for spectrally efficient communications in cellular systems
IEEE Wireless Communication Magazine, vol. 13, no. 4, pp. 56–61, Aug. 2006.[E. Björnson and E. Jorswieck]
Optimal Resource Allocation in Coordinated Multi-Cell Systems
Foundations and Trends in Communications and Information Theory, vol. 9, no. 2–3, pp. 113–381, 2013.
Mathematical description
![Macrodiversity mimo mac 2013](https://upload.wikimedia.org/wikipedia/commons/3/31/Macrodiversity_mimo_mac_2013.jpg)
The macrodiversity multi-user
MIMO
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 wir ...
uplink communication system considered here
consists of
distributed single antenna
users and
distributed single antenna
base stations (BS). Following the well established narrow band flat
fading
MIMO
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 wir ...
system model, input-output relationship can be given as
:
where
and
are the receive and transmit
vectors, respectively, and
and
are the macrodiversity channel
matrix and the spatially uncorrelated
AWGN
Additive white Gaussian noise (AWGN) is a basic noise model used in information theory to mimic the effect of many random processes that occur in nature. The modifiers denote specific characteristics:
* ''Additive'' because it is added to any nois ...
noise vector,
respectively. The power spectral density of
AWGN
Additive white Gaussian noise (AWGN) is a basic noise model used in information theory to mimic the effect of many random processes that occur in nature. The modifiers denote specific characteristics:
* ''Additive'' because it is added to any nois ...
noise is assumed to
be
. The
th element of
,
represents the fading coefficient (see
Fading
In wireless communications, fading is variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. Fading is often modeled as a random process. A fading channel is a ...
) of the
th constituent link
which in this particular case, is the link between
th user and the
th base station. In macrodiversity scenario,
:
,
where
is called the average link
gain giving average link
SNR of
. The macrodiversity power profile matrix
can thus be defined as
:
The original input-output relationship may be rewritten in terms of the macrodiversity power profile and so-called normalized channel matrix,
, as
:
.
where
is the element-wise
square root of
, and the operator,
, represents Hadamard
multiplication (see
Hadamard product). The
th element of
,
, satisfies the condition given by
:
.
It has been shown that there exists a functional link between the
permanent
Permanent may refer to:
Art and entertainment
* ''Permanent'' (film), a 2017 American film
* ''Permanent'' (Joy Division album)
* "Permanent" (song), by David Cook
Other uses
* Permanent (mathematics), a concept in linear algebra
* Permanent (cy ...
of macrodiversity power profile matrix,
and the performance of multi-user macrodiversity systems in fading.
Although it appears as if the macrodiversity only manifests itself in the power profile, systems that rely on macrodiversity will typically have other types of transmit power constraints (e.g., each element of
has a limited average power) and different sets of coordinating transmitters/receivers when communicating with different users.
Note that the input-output relationship above can be easily extended to the case when each transmitter and/or receiver have multiple antennas.
See also
*
MIMO
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 wir ...
**
Multi-user MIMO
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 cont ...
*
Antenna diversity
Antenna diversity, also known as space diversity or spatial diversity, is any one of several wireless diversity schemes that uses two or more antennas to improve the quality and reliability of a wireless link. Often, especially in urban and ind ...
*
Diversity scheme
In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by using two or more Channel (communications), communication channels with different characteristics. Diversity is mainly used in radio ...
s
*
Diversity combining Diversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal.
Various techniques
Various diversity combining techniques can be distinguished:
* Equal-gain co ...
**
Maximum ratio combining
** Selective combining
*
Diversity gain Diversity gain is the increase in signal-to-interference ratio due to some diversity scheme, or how much the transmission power can be reduced when a diversity scheme is introduced, without a performance loss. Diversity gain is usually expressed in ...
*
Microdiversity
*
Many Antennas
*
Multistatic radar
A multistatic radar system contains multiple spatially diverse monostatic radar or bistatic radar components with a shared area of coverage. An important distinction of systems based on these individual radar geometries is the added requirement f ...
*
Distributed antenna system
A distributed antenna system, or DAS, is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure. DAS antenna elevations are general ...
References
{{reflist
Antennas
Radio resource management