A Reliability Improved Routing as a Qos Measure for Mobile Ad-hoc Networks

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In the recent time, the huge growth in the use of the real-time applications for mobile devices has resulted in new challenges to design of protocols for mobile ad-hoc networks (MANETS). Most important among these challenges to enable real-time applications for MANETS which includes the support for quality of service (QoS), like bandwidth constraints and stability issues. Adding to this of course the reliability of the nodes as an important factor that has a direct effect on the network performance and data integrity. In this paper we will discussed the QoS main issue that affect several factors in the mobile ad hoc networks, which is the reliability. Because of the fact that the reliability and the availability of the nodes can be interacted made me use both the terms throughout the paper. we will suggest the reliable multi-path Quality of service routing (RMQR), (RMQR) as a QoS guarantee for the stability and reliability issues in the network. Next we will discuss the availability issues as a QoS guarantee and for this we will suggest the best suitable protocol which is “an efficient warning energy aware Clusterhead” WEAC as a solution to the availability issue. The two protocols will guarantee the availability and the reliability in mobile ad hoc networks as it is the new direction for routing algorithms design and it is a way to enhance the availability by controlling the Clusterhead based on its power level as a metric for availability as in WEAC protocol and the reliability by increasing the reserved bandwidth for the route as mentioned in RMQR protocol. Keywords-component; QoS, ad-hoc networks, RMQR, WEAC, Multi-path, MANETS, availability, Reliability. Introduction Most routing protocols for MANETs focus on finding a convenient route from a source to a destination without the consideration for utilization of the network resources or for the support of a specific application requirements, such as quality of service (QoS). Thus, the main problem of QoS is all about finding a route with the sufficient available resources, and the security and the stability of the routes that meet the QoS elements. those elements that will be considered in this paper:

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  1. Bandwidth estimation.
  2. Route discovery.
  3. Bandwidth reservation.
  4. Route selection.
  5. Route maintenance.
  6. Node availability.

For the first five point’s falls under reliability, I will suggest the RMQR protocol, for the last point (node availability) I will suggest the WEAC protocol with the suggested enhancement to the flows that it contains.

Establishing a reliable manet routing. The reason behing QoS: As said before, a mobile ad hoc network is a dynamic reconfigurable mobile wireless network that does not have a static fixed infrastructure. because of the high mobility of the nodes, the network topology of MANETs changes very rapidly, making it even more difficult to find a route that the packets use. QoS routing protocols supports real time applications such as video and audio communications. These protocols must create a route that satisfies some QoS constraints, such as delay, bandwidth and power . The suggested protocol review: The RMQR (reliable multi path QoS routing protocol) is suggested for the enhancement of the reliability issue; the suggested protocol is an on demand QoS aware routing protocol scheme. We will examine the routing problem associated with the searching for reliable multi- path QoS path from a source to a destination node in a mobile ad hoc network. It must also ensure certain bandwidth specifications. We calculate the route expiration time (RET) between two communicating mobile nodes by using global positioning system (GPS). Then using two parameters, the route expiration time and number of hops, in order to select a routing path with a low latency and high communication stability. Using GPS in LET calc. rmqr anatomy The mobility of the nodes in the MANETs is considered one of its’ main characteristics, and this will be present with frequent topology change. For this reason, the node, which frequently needs the network’s information for routing to be refreshed which is a source node in this case. also, there are so many limits on Mobile ad hoc networks, such as bandwidth and power. Therefore, calculating the path which satisfies the given bandwidth requirement of a quality of service guarantee is also difficult because, it is important to find a path that cannot only satisfy the QoS guarantee, but can also obtain Fig (2). Node threshold Fig (3). QRREQ packet delivery A highly fixed transmission and routing ratio during data transmission. Link expiration time calculation : As we said about the selected protocol that it has a mobility prediction for the nodes in the networks, this method will be introduced here. It will use the location information provided by the global positioning system.

To do that we will synchronize all the clocks of the nodes using the GPS clock, and for a mobile device, such as a notebook or a PDA having a GPS receiver, latitude and longitude can be calculated. The Knowledge of the parameters of motion for two nodes allows the calculation of the expiration of the link time that these two devices remain connected. And By matching the known latitude and longitude to the map, we can get the position. By always updating position, a GPS receiver can as well provide data for direction and speed of travel. We can assume that two nodes A and B are within the same transmission range r of each other. We let (X1, Y1) be the coordinate of mobile node A and (X2, Y2) be the coordinate of mobile node B. We let S1 and S2 be the mobility speeds and q1 , q2 (0£q,q£2P) be directions of motion as shown in Fig (1). And link expiration time can be calculated using the below equation [6]: D_t=-(qw+as)+√((q^(2+) a^2 ) (r^2-(qs-aw)^2)/((q^2+s^2 ) ) ) (1) Where q=S1cosq1-S2cosq2, w=X1-X2, a=S1 sinq1-S2 sinq2 and s=y1-y2. Now when a source sends a packet request, the request packet adds the node’s direction, location, and speed. The next hop of the source receives this packet request to predict the link expiration time between itself and the source. If node B is the next hop on the way of the packet for node A, node A appends its location information in the same packet. Thus, node B can calculate the connecting link expiration time between node A and node B [7]. Determining the bandwidth of the path: The assumptions of the network model are as follows. The (MAC) sub- layer in our designed model was implemented using the CDMA-over-TDMA channel model. this model is the same model as defined in Lin and Liu (1999). In CDMA-over-TDMA implementation, multiple sessions can also share the same TDMA slot using CDMA. CDMA can also be used to solve the hidden terminal problems. “the hidden terminal problem occurs when two nodes try to transmit to a common third node at the same time in that case a collision at this point will occur and it is a hidden terminal because one of the transmitted nodes is hidden respect to the other transmitted node because it is out of range and it is a problem due to the collision at the common node”. All the spreading codes are to be assumed orthogonal with respect to each other. We also used a transmitter-based code assignment in order to assign a code for each transmitter for data transmission purpose.

A spreading code can also be reused if any two nodes have a hop distance larger than two. An optimal code assignment scheme is considered to be operating at the lower layer of the system, and all the spreading codes are totally orthogonal with respect to each other. Thus, the hidden node problem can be avoided [10]. execution steps: I mentioned earlier the six points concerning the QoS. Now according to the first five, i will discuss the steps of the “RMQR” protocol. Route discovery: In this protocol, all the nodes monitor signals from their neighbors. Signal strength values can be calculated from the radio device and strength regulator average strength values. The strength of the signal is by SR and the range of the transmission of any node is expressed by R. The RMQR protocol defines the threshold value of the strength of the signal as shown in Fig (2), the threshold value for a node, thr = SR-a, where 0£ a £ R. If the signal strength received from the neighboring nodes is larger than or equal to thr value, the link from the neighboring node will be considered stable. Otherwise, the node will drop the packet. Each packet saves the history of the path and all link-state information. this information is delivered from the source to the destination. The destination node may also collect the link-state information from other QRREQ packets, each of those packets travels along different paths. For each request of bandwidth, a number of QRREQ packets may be sent. Each QRREQ packet will be responsible for searching a path from the source node to the destination. However, final paths at the end will be selected from all of the paths in which are utilized to the destination. The format of the QRREQ packet is shown below:

  1. TYPE: the packet type;
  2. S: the address of the source node;
  3. D: the address of the destination node;
  4. SEQ: the sequence number of the packet;
  5. NH: a list of nodes denoting the node history that records the path from the source to the current traversed node;
  6. FTS: free time slots nodes list, each list records free time slots among the current visited nodes and the last node recorded in the node history;
  7. BW: the requirement of the bandwidth from the source to the destination node.
  8. LI: the information of the location of mobile nodes that includes velocity, location and direction.
  9. LET: link expiration time list of links, each records the expiration time of the link among the traversed node and the last node recorded by the NH;

The LET represent the expiration time of the link between any two nodes, which is calculated using Eq. (1). Each node identifies its information of the location using GPS technology as shown in Fig (1). When one node receives a QRREQ packet, it will first check whether if the destination node address is in the QRREQ to determine whether the entry of the packet is its own address. If not, the node uses its location information in the packet and the location information in order to calculate the link expiration time. If we can predict the LET along each hop on the route, then we can predict the RET. The RET is defined as the minimum link expiration time in the routing path. Therefore, the RET will equal the minimum of the set of LETs for the entire route. The hop count “HC” is the total number of wireless links in the path. The location information of the destination node and the source node is included in the QRREQ packet in order to determine the LET value. Fig. (3) illustrates the concept of QRREQ packet delivery. We also assumed that the numbers besides arrows are LET of that link and numbers above vertices are the available slots for that same node. A node attempts to transmit the information to a destination node; it checks also its routing table to find the path which goes from source to the destination. If source node cannot find a path from a source to a destination, it will then initiate the routing discovery process.

Route reservation: In order to satisfy the bandwidth requirement and also taking in consideration large bandwidth as a QoS request, a bandwidth calculation of multi-path route is determined at the destination. It is also noteworthy that the QoS route is eventually calculated at the destination, depending on whether the network bandwidth is sufficient or not. Thus, we will describe here how to execute the path bandwidth calculation in the CDMA-over-TDMA channel model. Also, The path bandwidth is the set of available slots, between a source–destination pair. A possible path from the source node X to the destination node Y which may include several intermediate nodes, such as path (X, Y) ={X, B, C, M, Y}. The available bandwidth to the path, path_ BW (X, Y) is defined as: 〖path〗_BW (X,Y)=min⁡{〖link〗_BW (X,B),〖link〗_BW (B,C),…….,〖link〗_BW (M,Y)} (2) establishing an available manet To create a QoS guarantee environment in MANETS we need to focus on making the network available because availability reflects on all the other issues, for example from the definition of the quality of service we said it is about maintaining a certain level of performance. So if any of the nodes become not available the performance will be affected in apart or in a whole. From this point of view, we discussed (RMQR) protocol as a solution to maintain high level of stability in the routing and transmission ratio during a data transmission. In that point we will suggest (WEAC) WARNING ENERGY AWARE CLUSTERHEAD as a solution to the availability as it is one of our QoS issues. The reason behind the choice: As the first protocol fix the reliability issue for the links and guarantee a certain level of reliability with respect to the links, a question arises: what the next thing to do to guarantee the whole availability of the network? The obvious answer is to guarantee the availability of the nodes themselves, and the metric that will be used is the power level as the main metric for the nodes availability.

For this reason, the WEAC protocol is suggested in order to fix that issue. B. the Warning energy aware Clusterhead protocol: This protocol will establish a dynamic wireless mobile ad-hoc infrastructure, as in all cluster-based infrastructure protocols, in WEAC protocol a mobile node is elected from a nominee’s nodes to act as a base-station for some time within its zone. Prior to a previous study, the WEAC protocol scales very well for large networks of mobile stations and it also out performs other routing protocols in terms of load balancing, stability and energy saving among other networks. Another important issue relates to MANTEs, it may be considered as autonomous issue of mobile nodes. Some networks has a dynamic, sometimes rapidly changing multi-hop topologies, which are likely to be composed of relatively bandwidth limited wireless links. Hence an efficient centralized mechanism should be devised, and created, by a standard body when it is needed. As a consequence, a central standard authority is needed to carry out the important functions of routing and MAC in the wireless ad-hoc networks. Intuitively this place an indispensable focus of the infrastructure – based communications or cluster-based for the mobile ad-hoc networks. so designing an infrastructure based solution or protocol for infrastructure less is very important, as many ad-hoc problems will be solved that relate to the same issue. for the suggested system the above criteria made a great benefit as the nodes “people” are of rapid movement and the data “calls” are transferred from one cell to another, making the infrastructure – like criteria an important aspect to consider. from this perspective the weac protocol came to solve all the above issues with the react to topological change and load balancing. C. Operation : In this scheme some of the mobile terminals (MTs) are chosen in order to take responsibility of all the MTs within their own transmission range, or a group of them. Every MT will acknowledge its location using hello packet, sometimes are called beacon packets. The method of choosing a Clusterhead from a group of nominees is based on its power level “PL”.

MTs specification are as the following: a) a Cluster head: a leader of the cluster, as it is named. b) Zone_MTs: MTs are supervised by a Cluster head. c) Free_MTs: MT that is neither Cluster head nor zone MT (not related to a Cluster head). d) border or Gateway MT: that positions between the above, so it can be any one of them. Every MT will have a “much” variable an MT’s “much” variable will be set to the the Cluster head id. However, if that Mt itself is a Cluster head then its “much” variable will be set to a zero, else it will be set to -1 that will indicate that this node is a Cluster head of itself or it is a free node. A Cluster head will also collect complete status about other Cluster heads and their own list of MTs, and it will broadcast this status in its periodic “hello” messages. A Zone_MTs will accumulate information about their own neighbors using hello messages, and they will broadcast their own neighbor list to their neighbors using hello packets. MTs will announce their own ID with the periodic hello messages. a Mt will send a merge request to the other MT if the latter has higher PL and it should be larger than or equal to a THRESHOLD_1 as we will notice later. Also, the receiver of the merge request will respond with accept merge message and sets its “mych” variable to zero. When a MT receives the merge accept message it will set its “mych” number to the same id from the message came. D. Power level (PL) calculation technique: 1. mobile terminal PL ≥ THRESHOLD_1, a MT is willing to be Cluster head and ready to acknowledge other MTs merge request if those mobile terminals have a lower PL. if both have the very same power level (which is practically impossible) then the MT with a greater number of neighbors wins. As shown in fig (4). 2. THRESHOLD_1 < MT’s PL ≥ THRESHOLD_2, a mobile terminal will deny any merge request message that are requested by other MTs, if the MT serve as a Cluster head then it will remain Cluster head but it will not add any more nodes to its list of supervision. As shown in fig (5) below. Fig (4) PL≥ THERESHOLD_1 Fig (5) PL ≥ THERESHOLD_2 3. THERESHOLD (2) = MPT PL ≥ THRESHOLD (3), if an MT is serving as Cluster head, it sets its warning threshed flag to true, telling its zone MTs to look for another Clusterhead. They can remain until the threshold drain to THRESHOLD_3. As shown in fig (6). 4. mobile terminal PL = THRESHOLD (3), the Cluster head mobile terminal will deny any merge request and send a message to its zone MTs which is (iam_no_longer_your_ch) if it was serving other nodes. As shown in fig (7) At all times however if the MT mych = (-1) it will send a merge request to the MT with the higher PL that equals to THRESHOLD_1. Fig (6) PL > THERESHOLD_3 Fig (7) PL = THERESHOLD_3 conclusion I conclude from this study that to achieve a QoS guaranteed MANET we need to consider the most important QoS elements and acts accordingly, I combined two important aspects which are reliability and availability as an essential element to maintain a reliable, stable and available mobile ad-hoc network.

In this frame of study, we also saw that both the suggested protocols are based on the term availability, by maintaining the nodes availability according to their power level by suggesting the WEAC protocol. And the reliability by increasing the reserved bandwidth for the route as mentioned in RMQR protocol. future enhancements Starting with the QoS issues in MANETS, all of the considerations was based on obtaining reliability, stability, and availability, but very few had dealt with the quality of the transmission itself as well as the security of the path and the nodes themselves. It is an important research to establish because the ad-hoc networks have vast of application and can be applied in multimedia communication. A more emphasis is applied to the security of the links as it has a direct effect on the availability and integrity of the information transferred especially if the MANET was deployed in a military environment.

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