This article is a "division of labor movement edge computing" translation, mingled with some of my own understanding of
article background
to maximize the throughput is a key challenge for cognitive vehicle ad-hoc network (cvanet) in wireless applications face. Cooperative communication as a potential solution to increase link capacity through the use of space diversity in recent years has been widespread concern. However, if the link scheduling considered, this may be worse than the direct transmission mode transmission performance in end to end throughput.
Start the body
paper, a sensing cooperative communication link scheduling scheme for maximizing the throughput studies of C-VANETs.
Characteristics and authorization cooperative communication spectrum availability, we will extend the link synergistic link / Generic Link, defined extended link band for forming a three-dimensional (3-D) map of Conflicts to characterize these links the relationship between conflict.
Taking into account all the cooperation independent set figure, we set up an end to end throughput maximization problem mathematically, and the approximate optimal solution to this problem by linear programming.
Since the discovery np completeness of all independent sets, we also proposed pruning algorithm for sensing a cooperative communication link scheduling heuristics. Simulation results show that this scheme is an effective increase in the amount of end-fed method. With the increase of road infrastructure maturity and the number of motorists, road travel has become part of the United States and many other countries people's lives.
In VANET (VANETs), various onboard broadband communication applications will be widely used in the near future, these applications can provide entertainment for passengers to make long trips more enjoyable.
However, the proliferation of automotive applications beyond security needs additional resources to support radio, which makes licensed spectrum already crowded worse.
At the same time, these passengeroriented applications [1] [3], regardless of vehicle-to-vehicle (V2V) communications-based applications (for example, online games virtual meetings between different car passengers, file transfer, co-workers, etc. (such as web browsing, collaboration downloads, online video, etc.), the most critical and basic requirements, etc.) or vehicle-to-roadside (V2R) communication infrastructure is high-end data transfer throughput.
In VANETs Which one of the equally challenging task in view of VANETs demand for radio spectrum, the Federal Communications Commission (FCC) authorized to open the TV spectrum underutilized. Opportunity UHF television frequencies across the 470- 806mhz) [4], allow unlicensed users access.
Using a cognitive radio (CR) technology, vehicle / node (the words of the vehicle / node will be used interchangeably herein), and roadside units (RSU) VANETs empty opportunistic spectrum and may use these temporary licenses band / location, when / where the main service is not active. We call this VANET CR-capable of [3], [5] cognitive VANET (C-VANET). On the other hand, by using multiple antennas, such as multiple input multiple output (the MIMO), spatial diversity has been shown to reduce the error rate in terms of improving the power efficiency and throughput VANETs is effective. However, as wireless nodes equipped with multiple antennas is not always feasible.
In order to achieve spatial diversity without requiring a plurality of transmitting and receiving antennas, we can introduce a so-called cooperative communication in [6], [7]. FIG 1 [6], [7] can be a good example of three nodes illustrate the idea of cooperative communication illustrated in (a). In this subgraph node i to node j is transmitted by way of hop, cooperative relay node as a node r. Cooperative transmission from i to j is done on a frame by frame basis. In each frame, there are two time periods [1], [6], [8] - [10]. In the first slot (solid line), I make a transmission to destination j. Due to the broadcast nature of wireless transmission, I also heard the transmission relay node r. A second time period (dotted line), r j forwarding data heard at the groove. Therefore, cooperation and exchange, each node is equipped with a single antenna and antenna-dependent neighbors cooperation nodes to achieve diversity in space. If the selected relay node suitable partner, cooperation can effectively improve the communication capacity of the link [8], [11]. However, if we consider the link scheduling time frame-based, collaborative communication does not necessarily help to improve end to end throughput. Toys topology in (b) in FIG. 1 as an example. If the node i, then the link (i, j) will not be the link (u, v) directly to the interfering transmitting node j packets, so that they can be arranged simultaneously transmitted. Conversely, if (i, j) using r to perform cooperative communication, (i, j) will conflict with the (U, v), because the transmission cooperative relay node v to r (U, v) cause interference. Asaresult (i, j) and (u, v) can not be transmitted simultaneously, which may reduce the throughput from end to end to sr dt. In terms of throughput, to bring the benefits of cooperative communication may be offset, or even be scheduled simultaneously lost the opportunity to link more overwhelmed. Based on the above observation, C-VANETs throughput maximization problem of the emergence of several interesting question: when considering the uplink scheduling, whether there is an optimal method for cooperative communication brought to maximize throughput in the end benefits? whether to permit the availability of the band have any effect (ie, direct transmission or cooperative communication) and throughput? can we find in practice a simple and practical way to solve the problem of selecting a transmission mode?
To solve these problems, we propose a cooperative sensing communication link scheduling scheme, the objective is to maximize the throughput of a session in the C-VANETs. We let RSU scheduling multi-hop data transmission between the vehicles on the highway by sending a small control messages. Considering the availability of licensed spectrum, transmission mode and link scheduling and other factors, a mathematical model for maximizing throughput and near optimal solved by linear programming, we give a simple heuristic algorithm. Our outstanding contributions are summarized below.
• the characteristics of cooperative communication, we will use the new communication link cooperation extended to link cooperation. In order to maintain consistency symbol, we use a virtual cooperative relay and uses a direct transmission link will be extended to a common link.
• previous work by [12] - Inspired link conflict graph [16], we propose a three-dimensional (3-D) collaboration diagrams to describe the conflict interference relationship between the C-VANETs extended link. And [14] - a similar method used in [16], we each vertex in the graph are interpreted as basic resource scheduling point, and using the extended band link point representing each resource. Based on these extended links with right, we have established a three-dimensional cooperative conflict graph, redefined independent set cluster cooperation and conflict.
• by means of 3-D synergistic conflict graph, under the RSU may be a plurality of constraints (i.e., the availability of frequency bands, the transmission mode selection and link scheduling). All cooperation given independent sets of C-VANETs, the RSU may be an integer variable in the equation are relaxed optimization problem is solved by linear programming, the optimal end throughput between the source node and the destination node.
• Since the C-VANETs [13] - to find all the cooperation independent sets [17] np is complete, so we use a lot of maximum cooperation in conflict cliques, and developed a heuristic algorithm to approximate optimal pruning to-end throughput. Let us choose to extend RSU link for bandwidth and transmission, to the non-selected links to prune and update the link transmission time, until no further reduction in the maximum of all links link transmission time. The maximum throughput is estimated to be the inverse of a cluster of transmission time.
• by numerical simulation, we show the effect of the distance between the source node and the number of available frequency bands and the target node pair C-VANETs throughput performance.
We also show that
i) CR ability to use the cooperative communication creates more opportunities;
performance ii) cooperative communication link perceived better than scheduled transmission mode dependent scheduling;,
pruning algorithm iii) set forth in c - vanet to-end throughput close to optimal.
The rest of the paper is organized as follows. We review related work on maximizing throughput in the second section. In the third section, we will introduce C-VANETs settings and related models. Section 4 describes a three-dimensional co conflict graph, the concept of independent sets of group collaboration and conflict. In Section V, we mathematically describe the throughput maximization problem CVANETs in and near optimal solved using linear programming methods. In Chapter 6, we propose a cooperative communication link aware scheduling heuristic pruning algorithm. Finally, our performance results of Part VII simulation analysis, the conclusion of the eighth.
Part II: Cross-related work to maximize the throughput problem layer constraint (e.g., flow routing, link scheduling, etc.) has been extensively studied in the prior literature. Jain, who studied the effects of interference on wireless multi-hop network performance optimization based on np complete problems [18]. [13] Zhai and square studied given path channel capacity on link scheduling, using interfering cluster transmission time is designed routing metric is for single radio single channel (SR-SC) network, a high throughput path selection. For multi-radio multi-channel (multi-radio multi-channel, MR-MC) network, Li et al proposed a multi-dimensional (multi-dimensional, i.e., using the algorithm for optimal path capacity problems [14]. Different the mobile device with a radio network or SR-SC mc with a plurality of radio network, radio, but only one device CR radio is a software-defined [4], [19], [20], this should be a wide range of switching frequency range [21] - [23] in CR research community, it was also committed to cross-layer optimization .Tang et al [16] studied in a multi-hop R C network to maximize throughput and achieve a certain fairness to an Integrated spectrum allocation and link scheduling .Hou et al studied the combined frequency scheduling and routing problems to minimize network resources for the target range of spectrum in [24] proposes a centralized algorithm.
CR spectrum sharing for multi-hop network. Consider Spectrum uncertainty, pot et al [25] proposed licensing vacant band model for a series of random variables, it is a kind of CR network to a pair (α, β) parameters and minimize the use of unlicensed spectrum to support CR rate requires a certain level of confidence. Unfortunately, there is a lack of cross-layer design to maximize throughput, can not be effectively unified collaborative communications between wireless devices and the ability to CR devices. In cooperative communication, the study focused on information theory and communication theory problems. Liu et al [26] and Laneman in [7] on the main results of related topics were well investigated. Most studies common theme in this field is to optimize physical layer performance metric (i.e., from the perspective of the system in general, less concerned about the impact of cooperative communication network performance. For example, [27] and the Host-Madsen and Zhang [28 ] the Kramer, who studied the given source and rate of up to several cooperation programs and goals of diversity has to gain. based cascaded Nakagami fading [29], which provides a realistic description of the vehicle between the channels, Ilhan, etc. in human studies [1] in a cooperative diversity in VANETs, an auxiliary relay and proposes a scheme to optimize communication between the vehicle power distribution. Some pioneering work in cooperative communication networking and cross-layer design comprising the use of collaboration [30] the medium access control protocol, cooperative routing [10], [11], [31], the optimal cooperative relay selection [8] of the whole network, cooperative communication network coding [32], [33] VANETs using cooperative communication and [9] cross-layer routing. However, in consideration of VANETs joint coordinated communication link, and scheduling opportunistic spectrum access is a largely unexplored area of quantitative and qualitative .Pagadarai et al in [34] measured and characterized. Massachusetts interstate highway (I-90) free television spectrum along (470806 MHz), which paved the way for further study of C-VANETs In this work, we attempted to C-VANETs-end throughput maximizing comprehensive study, wherein selecting the transmission mode, the availability of spectrum and link scheduling are taken into account.
the third portion:
a, C-VANETs network settings
B, transmission model
1, amplify and forward
2, the decoding forwarding
3, direct transmission
us consider a C-VANETs [3], the plurality of [5] of the vehicle is operated in a different composition empty unlicensed band and the RSU (e.g., a base station (the BS), a gateway, an access point (the AP), etc.) is the group of nodes N = {1, 2, ··· N ···, N} ( a) highway, as shown in FIG. Let sr / dt represents the c - source / destination node vanet in session. Our goal is to maximize the throughput end of this session. Through a small vehicle with a control message exchange, RSU1 V2V communications can hop communication or multi V2R [5] scheduling transmission of large data packets. Taking into account the vehicle scheduling period τ is set to merge to enter / exit the highway and the availability of the band's permission. Suppose licensed spectrum band sb = {1,2, ···, b , ···, b} have the same bandwidth, the bandwidth of size w.
To distinguish c - two kinds of relay node [11] vanet in, we will relay nodes for cooperative communication is called cooperative relay, the relay node for the multi-hop relay traditionally referred to as multi-hop 2 relay. Taking into account the concept of cooperative communication, and hardware limitations inherent CR apparatus, we assume that each node has only one radio, but can be transferred to any of the available radio band of packet transmission. Each node uses some i∈N spectrum sensing techniques (e.g., [35], [36]) to identify a set of available, unlicensed frequency band occupied by the main business. The location of the node, the C-VANETs, the available frequency band of a node may be different from the other, as shown in FIG. Mathematical way, let Bi⊆ I representthesetofavailablelicensedbandsatCRnode∈N. Bi may be different of Bj, where j is not equal to i, and j∈N, i.e., it may be Bi̸ = Bj. For r cooperative relay link (i, j), we assume that the same transmission band from i to j, and j is transmitted to the r. Thus, we have B (i, r, j) = B (i, j) = Bi Bj. Further, the distribution divided by the period thersul 3 will be calculated within the time frame, if the cooperative communication, each time frame is equally divided into two transmission periods and transmission from i to j from r to j. In this section, we present expression data rates up in different transmission modes.
Based on these findings, we have two observations. First, the CAF (or CDF) compared with CDTx, cooperation is difficult to say the spread is always better than direct transmission. In fact, poor relay selection can be made up at the data rate lower than the direct transmission cooperative communication achievable data rate [8] under. Second, although the AF and DF are different mechanisms, but the ability to both have the same form, i.e., SNRij, SNRir SNRrj and function. Thus, one sensing link scheduling algorithm based on cooperative communication AF may well be extended to DF.
Therefore, only focus on one is enough, we select the AF in this article.
C, transmission and interference levels
Interference in a wireless network may be defined according to the protocol model or physical model [37]. In the protocol model [13], in [37], there is a fixed transmission range and interference range fixed, the interference range is generally 1.5 to 3 times the transmission range. This range may vary from two different bands. It represents the set T bi licensed band B (receive frequency band) of Bi, a set of neighboring nodes within transmission range of node i. For r for link (i, j) in cooperative communication band b, we have r = j and r T b (i, j) = T bi T bj. On the other hand, the relationship between the two conflicting links on the same frequency band may be determined by a specified interference range. Most of the work using the conventional protocol model [13], [14], [16], [24], [25], the interference on the network abstraction conflict FIG. Using the protocol model depicts c - link interference relationship between vanet in cooperative communication according to the characteristics of the three-dimensional extended conflict graph of Conflicts FIG. Details will be covered in the next section.
IV, c - in cooperation vanet FIG conflict, the conflict set and independent groups
In this section, we first link in the extended C-VANETs is associated with a particular characteristic (WRT) cooperative cooperative communication links / link universal . We then created a 3D collaborative conflict graph to describe the relationship between the interference of these extensions links. In addition, we redefine the set of independent and Group conflict [12], [13], to indicate when the c - vanet cooperative communication is involved, which can be activated at the same time the link, which link can not.
A, will be extended to link cooperation / common link
For a link (i, j), r is the node if its optimal cooperative relay, we calculate the cooperative communication achievable data rate (i.e., if CAF (i, r, j) > CDTx (i, j), we can then link (i, j) is extended (i, r, j), and (i, r, j) is defined as a coordination link. link symbol consistency, we use (i, φ, j) to represents a direct link transmission, [Phi] is a virtual cooperative relay, and define (iφj) generally link may be performed on the same C-VANET procedure for each link in the definition Rb (i, j) = { φ} T b (i, j). then, we can treat each link (i, j) to expand (i, r, j) in the form of a band b, wherein r Rb (i, j) Note that when RSU considering the relationship between the different interference and scheduling link transmissions on these links, links for cooperation link meet the conditions, the RSU can select it as a link or a universal link cooperation.
B. established based on FIG. 3D collaborative licensed band availability and conflicts cooperative communication characteristic
introduces a three-dimensional synergy conflict graph to characterize interference relationship between the C-VANETs plurality of links. more specifically, in FIG. 3D collaborative conflict G ( V, E), each corresponding to a vertex of the extended link belt, wherein the belt of the extended link is defined as ((i, r, j) , b) .linkband extended to show a link (i, r, j) effect. Note that operation in the frequency band b, which include the common link when r = φ cooperative relay, when the cooperation, including a relay contact r = φ. it also includes a special case of the cooperative communication in a single single-channel radio network available licensed band | B | = 1. If either of the following conditions is true, then the link is defined with two extensions of interference:
condition 1: two links with different extensions on the same node.
condition 2: If the two links with extended use of the same frequency band, when the receiving node or a relay node which cooperate with one or the other transmitting node interfere cooperative relay node, their transmissions will interfere with each other.
Under these conditions, the two will be the vertex V G (V, E) is connected to the free edges, if they correspond to the mutual interference with the link. For illustrative purposes, we give a simple example to illustrate how to construct a three-dimensional view of the conflict to cooperate. As shown in FIG 3 (a) represented by C-VANET toys, we assume that a vehicle equipped with CR 6 transceiver, i.e., A, B, C, D , E and F., And two licensed bands, i.e., level 1 and level 2. A source to a node, the node E for the target path. For link (A, B), we assume CAF (A, F, B) > CDTx (A, B). Thus, the RSU may be used as a relay node F together form a cooperative link (a, F, B). For link (B, C), we assume that the CAF (B, F, C) <CDTx (B, C), which means (B, C) does not extend to (B, F, C). For other links, they can be expanded to a general link, for example, (C, D) (CφD ). Depending on the geographic location of a currently available link extended frequency band may be the third - on the other of spreading different frequency bands mentioned in section a link. For example, the available band license group (φ, B) / (A , FB) {1}, the band set (A, φ, B, C ) {1,2}. In addition, we use the d (·) to represent the Euclidean distance.
Because any node has only one radio, and can only work on one band.
The presence of one side ((A, φ, B) , 1) between the vertex and ((A, F, B) , 1), since they are the same transmitting and receiving nodes (also satisfies Condition 1) but with different transmission mode. When the transmission schedule RSU, can choose to use ((A, φ, B) , 1) or ((A, F, B) , 1).
Note cooperative communication may increase the achievable data rate of the link, but it can also bring additional interference. As shown in FIG 3 (b), if one pair of cooperative linkband shown ((A, F, b) , 1) RSU is selected, the conflict ((A, φ, b, C), 1), ((A, φ , b, C), 2) , ((1 C, φ, D)) and ((DφE), 1). In contrast, if the link-band of the general ((φ, B), 1 ) is employed, the conflict ((φB, C), 1 ), ((φB, C), 2) and ((1 C, φ, D)). This is because, when the partnership link transmission frequency band of the plan, we must also consider the nodes within interference range of node and relay node F of cooperation within interference range of the transmitting node A.
C. independent set and the cooperation of factional conflict
analysis indicates a c - 3D Collaborative vanet conflict graph of G = (V, E), we will affect the vertex u vertex V VV described below
Wherein two vertices corresponding to a link with two pairs. If there is a vertex / extension link-band setI V and the extension link-band u I meet me, u = V wuv <1, the transmission link-band dual u will be successful, even if other link-band belonging to the set I are transmitted simultaneously. If any of u I satisfy the above conditions, we may schedule transmissions on the links with all of these extensions in I, while it is active. Such a vertex / extended cooperation independent set of link band set I referred to. If a further increase in the extension of a link in cooperation SETI separate frequency bands will produce a non-independent setI, I is defined as a set of maximum co
Furthermore, if there is a vertex / extended link with any of the V and with two extension links in Z u and V to satisfy wuv = 0 (i.e., the vertices u and v can not simultaneously transmit), Z is called cooperative conflict Group. If Z adding any link with an extension of the conflict is no longer a cooperative group, then Z is defined as a maximum co-conflict group.
Fifth, the high-end throughput cooperative communication link perceived optimal scheduling
After building a three-dimensional synergy conflict graph, first discussed in this section C-VANETs wrt selected relay link scheduling may collide. Then, we discuss how to calculate the channel capacity constraint-based routing and description streams of a single radio node. According to cross-layer constraints, the establishment of a c - mathematical model for maximizing throughput vanet, and using linear programming methods are approximate optimal solution.
Before discussing the cooperative communication link scheduling perception, we need to clarify two issues with the relay selection wr.t link scheduling conflicts related. Introduces two relay selection conflict [11], the cooperative multi-hop wireless communication network is introduced. The first choice is coordinated and multi-hop conflicts between choices. (Selected as cooperative relaying node and a multi-hop relay), in Case 1 and Case 4 shown in Figure 2; two selected cooperative relay conflict between the different links. (Different from the same node as the link selection cooperative relay), in the case 4 as shown in FIG. If the network is only one frequency band is available, it is easy to prove relay selection wrt link scheduling conflicts will never occur.
However, if there are a plurality of frequency bands available in the network (e.g., C-VANETs), then there are two kinds of collision, as shown in FIG. Fortunately, it can be well described by all three of Conflicts FIG relay selection conflict C-VANETs (e.g., three cases of FIG. 4 satisfy the interference condition 1), so that it can be used RSU sensing coordinated communications link Road schedule.
Note that a C-VANETs node may share a case where at different times, to switch between the nodes and the cooperative multi-hop relay, which is [11] fixed character different nodes.
. . .
. . .
Where (16), (17), (18) and (19) requires that each node have at most one nonzero flow outgoing link, and there RSU selected path between the source and the target; (20) and ( 21) shows that (i, r, j) on the traffic flow can not exceed the capacity of the link extension, coordinated communication capacity of the section indicated by VB-aware link scheduling obtained. Notice that I've included all the separate collection in C-VANETs in. Givenallindependentsets6 inthenetwork wefindthattheformulated optimization is a mixed-integer linear programming problem because δij only binary values. It may be some typical algorithms (e.g., [24], [25], branch constraints, and [39], etc.) or software (such as CPLEX [13], [40] , LINDO , etc.) is approximately optimally solved in polynomial time as long as all the cooperation can be independently set in G (V, E) be found.
VI.Cooperation communications aware scheduling heuristic pruning algorithm
iteration of link with pruning algorithm
1, the establishment of three-dimensional co-conflict graph
2, look for the biggest faction conflicts
3, the transmission time calculated conflict Group
4, the greatest conflict cooperation sort faction
5, a high throughput selected optimum bandwidth
6, trimming cooperation / generic link band to
7, and the estimated throughput iterative process
throughput calculated
Conclusion:
This paper studies the problem of multi maximize throughput under the constraints of C-VANETs. (CR inherent single radio equipment constraints, availability of licensed spectrum, transmission mode selection and link scheduling). Considering the particularity of cooperative communication, the link is first extended, the link can be divided into synergistic / Generic Link. Then, according to the available frequency band on the different spreading link, it defines an extension link frequency band, and construct a three-dimensional diagrams to describe the conflict Conflict cooperative relationship between these extensions link band pair. On this basis, we have established a mathematical model to-end throughput maximization problem. For C-VANETs cooperation in all independent sets, we can optimize the relaxation of the issues raised, and the approximate optimal solved by linear programming. Np found for the completeness of all independent sets of proposed pruning algorithm for sensing a cooperative communication link scheduling heuristics. By simulation, we show that
: i) CR using cooperative communication capability creates more opportunities
ii) selecting the appropriate link scheduling performance than relying solely on the transmission mode transmission mode (cooperative communication or direct transmission) chain Road scheduling performance.
