CN102281130B - Fractional frequency reuse (FFR)-based multi-cell cooperative multiple-input multiple-output (MIMO) system - Google Patents

Abstract

The invention discloses a fractional frequency reuse (FFR)-based multi-cell cooperative multiple-input multiple-output (MIMO) system, and belongs to the field of cellular wireless communication. The system comprises at least one hyper MIMO cluster (HMC); each HMC comprises an internal cooperative MIMO cluster and external cooperative MIMO clusters; the external cooperative MIMO clusters are circumferentially arranged along the outer edge of the internal cooperative MIMO cluster; the same frequency is used in the internal cooperative MIMO cluster in each HMC; different frequencies are used in the adjacent external cooperative MIMO clusters of each HMC; and different frequencies are used in all cooperative MIMO clusters in each HMC. Because an FFR-based frequency distribution mode is adopted in the cooperative cellular system, compared with a full frequency multiplexing system, higher channel capacity can be acquired. In addition, elimination of co-channel interference among the clusters is realized without depending on certain pre-coding technology based on the cooperation of the MIMO clusters, so the FFR-based multi-cell cooperative MIMO system can be used in both uplink and downlink systems.

Description

Many honeycombs cooperation mimo system based on FFR

Technical field

The present invention relates to a kind of cooperation of many honeycombs based on FFR mimo system, belong to the cellular radio Communication field.

Background technology

Along with the propelling of social informatization, mobile multimedia and mobile Internet etc. is engulfed the wireless application fast development of massive band width, constantly challenges the performance boundary of existing wireless communications network.Although by advanced technologies such as error correcting code with better function and Adaptive Modulation, systematic function is increased substantially, make the interference between the limited root problem of Cellular Networks capacity-co-channel user, still do not solve.And along with the increase of number of users, in Cellular Networks, the density of base station also improves constantly, and forces in Cellular Networks of future generation and adopts frequency multiplexing mode more closely, and co-channel like this interference particularly highlights the bottleneck effect of cellular system performance.

The many honeycombs cooperation MIMO(multiple-input multiple-output multiple-input and multiple-output that occurs in recent years) technology provides a kind of possibility for the solution of co-channel interference problem, and in the new generation of wireless network standards such as LTE-Advanced by extensive discussions, simulation study shows that many honeycombs cooperation MIMO technology all increases in many-sides such as coverage, cell edge throughput, reliability and spectrum efficiencies to whole network performance.

At present, consider that based on the design of many honeycombs cooperation mimo system all base stations in network all use same frequency to form a MIMO bunch of situation of cooperating, the co-channel interference problem in whole MIMO bunch just can solve by the processing of the allied signal between base station so more.But for certain wireless cellular network that is formed by hundreds and thousands of base stations, if form a huge MIMO bunch, in bunch between base station the expense of the information exchange such as user data and channel status huge, and the signal in this bunch process also can be very complicated.So can only consider in reality to form a virtual cooperation MIMO bunch with limited honeycomb, all users use same frequency in this MIMO bunch, so just need to cover certain larger zone with a plurality of MIMO bunch, such as with some, by 3,7 or 19 cooperation honeycombs, as an elementary cell, covering whole zone,, if these MIMO bunch use identical frequency, also can interfere with each other.

(this figure is from J.Zhang as shown in Figure 1, R.Chen, J.G.Andrews, A.Ghosh, and R.W.Heath Jr., " Networked MIMO with clustered linear precoding; " IEEE Trans.Wireless Commun., vol.8, no.4, pp.1910 – 1921, Apr.2009).In this scheme, proposed a kind of based on the multiplexing cooperation honeycomb a network implementation of the descending full rate of MIMO bunch of b, co-channel interference in eliminating bunch by the abundant cooperation between MIMO bunch of inner base station, simultaneously also carry out certain cooperation between each MIMO bunch, the co-channel interference between bunch edge customer is eliminated in advance.

at present people have carried out more concern to the design based on virtual MIMO bunch in downlink honeycomb system as shown in Figure 1, in downlink system because the position of base station be determine and also base station between can communicate by letter by high-speed link, some precoding techniques that therefore can be undertaken by cooperation between base station are such as DPC(dirty paper coding) and block diagonalization etc. disturb inhibition, and in up-link, because user's position is generally random distribution in each residential quarter, and also be difficult between the user exchange, therefore these interference mitigation technologies are very awkward in up-link.

In addition, in these existing designs based on virtual MIMO bunch, consider each MIMO bunch in and use the full rate multiplexed network of same frequency between each MIMO bunch, and we find by research, the interference between MIMO bunch of frequency can make the channel capacity of this network significantly descend together.

Summary of the invention

, in order to solve the problems of the technologies described above, the present invention proposes a kind of cooperation of many honeycombs based on FFR mimo system.This system is in the situation that the honeycomb number in cooperation MIMO bunch is limited, the reuse based on FFR(fractional frequency has been proposed, fractional frequency reuse) cooperation MIMO clustering architecture is realized the compromise that cellular network design intermediate frequency spectrum utilance and co-channel interference suppress, thereby obtains to compare larger channel capacity with the full rate multiplex system.

The present invention mainly protects and a little has been to propose in the Cellular Networks based on the virtual cooperation MIMO technology of FFR and the distribution method of total bandwidth in MIMO bunch of system, and concrete technical scheme is as follows:

The present invention includes at least one HMC, described each HMC comprises inner cooperation MIMO bunch and outside cooperation MIMO bunch, the outer rim circumferential arrangement of described outside cooperation MIMO bunch along described inner cooperation MIMO bunch, MIMO bunch of identical frequency of use of inside cooperation in described each HMC, between described each HMC, adjacent outside cooperation MIMO bunch is used different frequencies, uses different frequency between MIMO bunch of inner all cooperations of each HMC.

In described HMC, total honeycomb is counted NHMC and will be met the condition of seamless coverage, i.e. N _HMC=i ²+ j ²+ ij, i wherein, j is the integer greater than 0.

Described outside cooperation MIMO bunch further meets following requirement: the honeycomb number of plies N in described outside cooperation MIMO bunch _CL〉=1, the number N of honeycomb increases gradually since 2 in described outside cooperation MIMO bunch, and carries out channel capacity for each N value and calculate, until obtain the system channel capacity of expecting; If can not meet the demands increase total honeycomb number in HMC.

The distribution principle of the total bandwidth of the described cooperation of many honeycombs based on FFR mimo system between inner cooperation MIMO bunch, each outside cooperation MIMO bunch is as follows: the bandwidth of distributing in establishing described inner cooperation MIMO bunch is B _IN, the bandwidth in each outside cooperation MIMO bunch equates, is B _OUT, the total bandwidth of the system of setting up departments is 1:

$\left\{\begin{array}{c}{B}_{\mathrm{IN}}{C}_{\mathrm{IN}}/N_{\mathrm{CIN}}=B_{\mathrm{OUT}}{C}_{\mathrm{OUT}}/N_{\mathrm{COUT}}\\ B_{\mathrm{IN}}+{\mathrm{NB}}_{\mathrm{OUT}}=1\end{array}\right.$

In following formula: C _INFor the channel capacity in MIMO bunch of each inside cooperation, C _OUTFor the channel capacity in each outside cooperation MIMO bunch, N _CINFor the cooperation honeycomb number in each inside MIMO bunch, N _COUTFor the cooperation honeycomb number in each outside MIMO bunch, N is the number of outside cooperation MIMO bunch.

In terms of existing technologies, advantage of the present invention is: adopted the frequency distributing mode based on FFR in the cooperation cellular system, can obtain to compare larger channel capacity with the full rate multiplex system.Between not needing in the present invention in addition to realize bunch by some precoding techniques that the cooperation between each MIMO bunch is carried out, co-channel interference is not eliminated, and therefore can use in the uplink and downlink system.The present invention fully cooperates in each cooperation MIMO bunch, and does not need to cooperate between MIMO bunch of each cooperation, so system is relatively simple, and it is convenient to realize.

Description of drawings

Fig. 1 is that cooperation honeycomb number is 7 full rate multiplex system schematic diagram;

Fig. 2 is that single HMC forms schematic diagram;

Fig. 3 is N _CIN=7, N _COUT=6, N _CL=2, N _HMC=37 HMC forms schematic diagram;

Fig. 4 is with N _HMC=37 HMC is the cellular network schematic diagram of cell formation;

Fig. 5 is that the corresponding channel capacity of HMC structure shown in Fig. 3 and other two kinds of cooperation MIMO structures compares.

Embodiment

For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

In the present invention, the FFR thought based on single honeycomb is expanded to based in the cellular system of virtual cooperation MIMO bunch.Be to disturb littlely between the user of neighbor cell inside based on the FFR mentality of designing of single subdistrict, can adopt full rate multiplexing, and the interference between the neighbor cell edge customer be larger, need to use different frequencies.Of the present invention based on the FFR system of MIMO bunch in, as shown in Figure 2, each hyper MIMO cluster(HMC) by an inner cooperation MIMO bunch MC _INWith N outside cooperation MIMO bunch MC _{OUT_1}... MC _{OUT_N}Form, whole network covers as elementary cell by this HMC.In each HMC, all use same frequency in inner MIMO bunch, use different frequency between adjacent outside cooperation MIMO bunch between each HMC, the total honeycomb in HMC is counted N in addition _HMCMeet the condition of seamless coverage: N _HMC=i ²+ j ²+ ij, i wherein, j is the integer greater than 0.

Cooperation mimo system design principle based on FFR:

In the cellular network based on cooperation MIMO technology, the cooperation channel capacity gain of system becomes greatly with the increase of cooperation honeycomb number in MIMO bunch, and on the other hand, the complexity of system and intercommunication expense also increase thereupon.Therefore we wish to obtain enough large channel capacity gain under the as far as possible little prerequisite of the honeycomb number of cooperation.Therefore at first need the channel capacity of certain cooperative network structure is calculated, computational methods and document 1(Piao high aim, Wang Zhaocheng, Yang Zhihang, " based on the ascending honeycomb system channel capacity of cooperation MIMO and fractional frequency reuse ", Tsing-Hua University's journal, 2011,51 (3), the computational methods of describing in 158-163) are identical, if can not meet the demands need to increase total honeycomb number in HMC.

If the cooperation honeycomb number in each inner MIMO bunch is N _CIN, the honeycomb number in each outside MIMO bunch equates to be N _COUT.In order to make in adjacent HMC the co-channel interference between inner MIMO bunch enough little, it is enough large that the distance between them is wanted, so form the honeycomb number of plies N of outside cooperation MIMO bunch _CLMeet N _CL〉=1.On the other hand, in order to make the co-channel interference between outside MIMO bunch enough little, with the interval between MIMO bunch is also enough large frequently, therefore the number of MIMO bunch of the outside cooperation of N() can not be too little, but in order to obtain enough cooperation mimo channel capacity gain, cooperation honeycomb number in each outside MIMO bunch again can not be too little, therefore N can not be too large (after the inside and outside cooperation honeycomb number of plies is determined, the selection of N can increase gradually since 2, and carry out channel capacity for each N value and calculate, until obtain the system channel capacity of expection).Therefore at first need the channel capacity of certain cooperative network structure is calculated (computational methods can find in pertinent literature 1), if can not meet the demands need to increase total honeycomb number in HMC, the cooperation honeycomb number in then according to mentioned above principle, selecting inside and outside MIMO bunch.

Obviously, the channel capacity of this system is relevant with the method for salary distribution of total bandwidth in inside and outside cooperation MIMO bunch of system.In existing relevant design, the average and principles data transfer rate maximum of whole network that adopt are carried out the resource distribution of system more, but have ignored the fairness between the user in this principle.Adopt the principle that equates based on every user's ergodic capacity in the present invention.If the bandwidth of distributing in inner MIMO bunch is B _IN, the bandwidth in each outside MIMO bunch equates, is B _OUT, the total bandwidth of the system of setting up departments is 1:

$\left\{\begin{array}{c}{B}_{\mathrm{IN}}{C}_{\mathrm{IN}}/N_{\mathrm{CIN}}=B_{\mathrm{OUT}}{C}_{\mathrm{OUT}}/N_{\mathrm{COUT}}\\ B_{\mathrm{IN}}+{\mathrm{NB}}_{\mathrm{OUT}}=1\end{array}\right.---\left(1\right)$

C wherein _INAnd C _OUTBe respectively the channel capacity in each inner MIMO bunch and outside MIMO bunch.

The availability of frequency spectrum at the cooperation honeycomb that is arranged in each HMC inside bunch is 1, and the availability of frequency spectrum of cooperation honeycomb bunch that is arranged in the HMC edge is greater than 1.

Embodiment:

One, the structured flowchart of the exemplary embodiment of the system of this invention

Now with N _CIN=7, N _COUT=6, N _CL=2, N _HMC=37 HMC structure is described in detail as an exemplary embodiment.

As shown in Figure 3, this HMC is by 1 inner MIMO bunch and 5 outside MIMO bunch (totally 37 honeycombs) formation.Cell wherein ₁-cell ₇These 7 center honeycombs form inner cooperation MIMO bunch, frequency of utilization f ₁Outside MIMO bunch consists of 2 layers of adjacent honeycomb, and they evenly are divided into 5 MIMO bunch, and the cooperation honeycomb number in each bunch is 6, wherein cell ₈, cell ₉, cell ₃₇, cell ₂₀-cell ₂₁These 6 edge honeycombs form outside cooperation MIMO bunch 1, frequency of utilization f ₂, similarly, cell ₁₇-cell ₁₉, cell ₃₄-cell ₃₆These 6 edge honeycombs form outside cooperation MIMO bunches 5, frequency of utilization f ₆, then with this HMC copy to form whole network, as shown in Figure 4.The present invention between each HMC, is positioned at cooperation MIMO bunch of inner use same frequency, is positioned at the outside cooperation MIMO bunch of adjacent use different frequency at edge.Certainly, inner at each HMC, use different frequency between all cooperation MIMO bunches.Honeycomb number in each outside cooperation MIMO bunch can be identical, also can be different., for convenience of calculation, selected identically in the present embodiment, can adjust according to specific circumstances in actual design, selected different.

Adopt the starting point of the HMC structure in Fig. 4: by the research in early stage, we find the co-channel interference honeycomb that the channel capacity of certain MIMO bunch is exerted an influence, and the distance of MIMO bunch is main relevant with the propagation loss factor of n in channel therewith, increase along with n, the same frequency honeycomb number of plies that the channel capacity of certain MIMO bunch is affected to some extent reduces gradually, such as when the n=2, need to consider adjacent 4 layers of interference with the frequency honeycomb, and when n=4, the same frequency honeycomb that produces major effect is nearest 2 layers.In Fig. 4, for adjacent HMC, the honeycomb number of plies of on average being separated by between inner cooperation MIMO bunch (7 honeycombs, consisting of) is greater than 4, thereby can ignore the co-channel interference between them; And for the MIMO bunch of outside, with cell ₈, cell ₉, cell ₃₇, cell ₂₀-cell ₂₁MIMO bunch that forms is example, if consider 4 layers with interior interference with the frequency honeycomb, its honeycomb that exerts an influence only is cell ₈₆And cell ₉₇.Therefore by this structure, co-channel interference was reduced greatly, and can obtain again certain cooperation MIMO gain, thereby obtain larger channel capacity.

We have also proposed a kind of combination of network structure based on cooperation MIMO and fractional frequency reuse in document 1 in addition, yet during the system in this literary composition, frequently resource to distribute what adopt be the average and maximum principle of data transfer rate of whole network, do not consider the fairness between the user, if and with the equal principle of each user's ergodic capacity, every user's ergodic capacity that the structure in this document 1 obtains is much smaller than the HMC structure shown in Fig. 4.We are in Fig. 5 during to the principle that equates according to every user's ergodic capacity, the multiplexing corresponding every user's ergodic capacity of cooperation MIMO structure (cooperation honeycomb number is 7) of cooperation MIMO structure shown in the structure of HMC shown in Fig. 4, document 1 and full rate compares, curve 1 is HMC structure shown in Figure 4, curve 2 is full rate multiplexed MIMO (cooperation honeycomb number is 7), and curve 3 is document 1 cooperation MIMO used structure.Provided in Table 1 calculating parameter.

Calculating parameter setting in table one Fig. 5

Parameter	Value
		The honeycomb radius, R	1.0km
Operating frequency, f	800MHz
		Reference distance (calculating the free space reference power), d 0	100m
Antenna for base station	N BS=1,G r=1,H BS=100m
		User antenna	N UT=1,G t=1,H UT=1.8m
Transmitting power, P t	26-41dBm
		The propagation loss factor, n	3
The thermal noise spectrum density	-174dBm/Hz
		User distribution	Evenly
Subcarrier spacing, B sub	4kHz

Above a kind of cooperation of many honeycombs based on FFR mimo system provided by the present invention is described in detail, applied specific embodiment herein principle of the present invention and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously,, for one of ordinary skill in the art,, according to thought of the present invention, all will change in specific embodiments and applications.In sum, this description should not be construed as limitation of the present invention.

Claims (2)

1. the cooperation of the many honeycombs based on a fractional frequency reuse FFR mimo system, is characterized in that, comprises at least one HMC (hyper MIMO cluster), and described each HMC is by 1 inner cooperation MIMO bunch MC _INWith N outside cooperation MIMO bunch MC _{OUT_1}... MC _{OUT_N}Form, described each inner cooperation MIMO bunch by N _CINIndividual cooperation honeycomb forms, and described each outside cooperation MIMO bunch by N _COUTIndividual cooperation honeycomb forms, honeycomb number in each outside cooperation MIMO bunch is identical, and the outer rim circumferential arrangement of described outside cooperation MIMO bunch along described inner cooperation MIMO bunch is inner at described each HMC, use different frequency for avoiding interference between the MIMO of all cooperations bunch, in described HMC, total honeycomb is counted N _HMCMeet the condition of seamless coverage, i.e. N _HMC=i ²+ j ²+ ij, i wherein, j is the integer greater than 0; Between each HMC of described many honeycombs cooperation mimo system, be positioned at the cooperation MIMO bunch of inner frequency that use is identical, be positioned at the outside cooperation MIMO bunch of adjacent frequency that use is different at edge, whole network covers as elementary cell by described HMC.

2. a kind of cooperation of many honeycombs based on fractional frequency reuse FFR mimo system as claimed in claim 1, it is characterized in that: described outside cooperation MIMO bunch further meets following requirement:

Honeycomb number of plies N in described outside cooperation MIMO bunch _CL〉=1;

In described outside cooperation MIMO bunch, the number N of honeycomb increases gradually since 2, and carries out channel capacity for each N value and calculate, until obtain the system channel capacity of expection; If can not meet the demands increase total honeycomb number in HMC.

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