Round robin based Secure-Aware Packet Scheduling in Wireless Networks

Download (1)

Full text


Round robin based Secure-Aware Packet

Scheduling in Wireless Networks

Arun Raj

School of Computer Science and Technology, Karunya University, Coimbatore, 641114, India

P. Blessed Prince

School of Computer Science and Technology, Karunya University, Coimbatore, 641114, India


Packet scheduling algorithms enhances the packet delivery rate effectively in wireless networks; it helps to improve the quality of service of the wireless networks. Many algorithms had been deployed in the area of packet scheduling in wireless networks but less attention is paid to security. Some algorithms which offer security often compromise performances such as schedulability, this is not desirable. This performance problem will become worse when the system is under heavy load. In this paper we propose Round robin based Secure-Aware Packet Scheduling algorithm (RSAPS) for wireless networks which focuses on secure scheduling. RSAPS is an adaptive algorithm which gives priority to scheduling when system is under heavy load. Under light load RSAPS provide maximum security for the incoming packets. Simulation has been performed using the proposed method and compared with existing algorithms SPSS and ISPAS. And it is found that RSAPS shows excellent scheduling quality holding the security levels.

Keywords: algorithms; packet scheduling; round robin; secure-aware; wireless networks. 1. Introduction

The technological advancement in the society made computer networks a vast and demanding research area, every organization currently rely on computer networks for data communication. Computer networks in the current scenario forms the back born of every industry and also for the public sector. Computer networks can broadly classified into two: wired networks and wireless network. Wireless networks in recent years receives greater attraction since it is widely deployed in public places such as libraries, hotels, schools and airports due to the greater flexibility, increased efficiency, and reduced wiring costs [4]. Wireless networks have been proved useful in area where there is lack of infrastructure. Use of wireless networks has helped various organizations to be mobile and have given users the freedom to get connected even when one is travelling. Our everyday mobile phone network is an example of a huge wireless network.

There are various kinds of wireless networks available for various different applications. We discuss the four broad categories namely wireless PAN, wireless LAN, wireless MAN and wireless WAN.

Wireless Personal Area Networks (WPAN): WPAN as the name suggests, it is used for connecting small number of devices within a small range. Example infra-red and Bluetooth can connect a laptop to a headphone.

Wireless Local Area Networks (WLAN): WLAN provides connectivity between a laptop and any other device that have Wi-Fi to an access point which can provide access to internet. OFDM or spread-spectrum technologies enable clients to move within a local coverage area while remaining connected to the LAN.  Wireless Metropolitan Area Networks (WMAN): WMAN can connect high speed multiple wireless

LANs that are geographically close. Two or more nodes can communicate with each other as if they belong to the same LAN by using WMAN.

Wireless Wide Area Networks (WWAN): WWAN network usually covers large areas, i.e. connects different WLANS with the help of different cellular technologies such as LTE, WiMAX, CDMA, UMTS, and GSM. The speed of connection in such network depends on the cost of connection, which will increases with increasing distance. The most commonly available WWAN is internet [3].


other protocols aim to reduce the energy consumption and some others also provide security. One area which still remains under research is that of packet scheduling.

As the devices used in a wireless networks are light weight terminals the memory storage and buffer size will be limited. Due to the mobility of nodes there is always a problem of lost connections and thus loss of packets, in such situations one needs to maintain the packet for retransmission. Thus the problem of assigning packets to queues and determining which packet will be processed first; is a major challenge. Packet scheduling also refers to the decision of dropping not so urgent packets. The scheduler will drop the packets based on certain parameters such as network bandwidth, packet arrival rate, deadline of packet and packet size. Packet scheduling is important as it improves the performance of the network, efficient delivery of packets, improved transmission rates and saves energy in a wireless network.

In order to protect the data transmitted over a wireless channel may several international wireless organizations and wireless equipment providers have put forward some security standards for wireless networks, and the most common are WPA, WEP and 802.1X but a dynamic algorithm for providing security for wireless networks is still in search. In this paper we present a round robin based secure-aware packet scheduling algorithm RSAPS based on the algorithm proposed by Qin et al. 2008 [7].

The decision to process or drop packets is made by the scheduler based on the packet scheduling algorithm being used. Various scheduling algorithms that are widely used are Priority scheduling algorithm, round Robin scheduling algorithm and Greedy scheduling algorithm.

Priority Scheduling: In this scheme the packets are processed according to their priorities. Higher priorities are given to control packets.

Round robin Scheduling: in here the scheduler process the packets based on flows. Each flow is allowed to send one packet at a time.

Greedy scheduling: A greedy scheduling algorithm is where each node sends its own packet first before forwarding another nodes packet. The other nodes packets are schedule based on FIFO order [1].

The rest of this paper is organized as follows: related work is reviewed in Section 2. Section 3 presents the round robin based secure-aware packet scheduling model. Section 4 describes the RSAPS algorithm and the main principles behind it. Simulation experiments and performance analysis are presented in Section 5. Section 6 concludes the paper.

2. Related Works

Xiong et al. proposed a bidirectional concurrent transmission model and a packet scheduling problem to formulate centralized scheduling in WiMAX mesh networks which will effectively reduce the number of time slots required to transmit packets. Spatial reuse can improve the performance of wireless mesh network, the proposed algorithm make use of spatial reuse. Bidirectional concurrent transmission for WiMAX network was primarily proposed in this paper [8].

Hassan et al. proposed a fair-scheduling algorithm which delivers better performance in terms of the end-to-end delay experienced by the video frames. The system is based on the occupancy of the video decoder buffer. A base-mobile stations’ joint multi queue scheduling scheme that conserves a separate queue for each priority group and tries to enhance the performance of the high priority requests is being deployed [2].

Kensaku et al. proposed a packet scheduling scheme achieving max-min fairness without changing the existing IEEE 802.11 medium access control (MAC) protocol. A probabilistic packet scheduling scheme attaining max-min fairness is proposed as number of nodes increases the overall throughput significantly reduces due to the hidden-node problem [5].

Zhang et al. proposed a packet scheduling algorithm which aims at providing maximum downlink throughput when packet fragmentation is not allowed. It deals with the packet scheduling problem in wireless LANs with the One- Sender-Multiple-Receiver (OSMR) transmission technique OSMR allows the Access Point (AP) to send discrete packets to multiple nodes simultaneously [11].

Liu et al. proposed a Signal-Noise-Ratio (SNR) based algorithm i.e., Improved SNR-based Packet Scheduling (I-SPS) algorithm which aims to achieve better QoS for synchronous connections. In this algorithm connection with better channel condition will be assigned higher weight in scheduling and the connection writhed from burst error will be provided with higher weight after its channel condition becomes good. The proposed algorithm adaptively controls the service allocation in conflict with the signal-to- noise (SNR) fluctuation. The key point of the scheduling algorithm is dynamic amendment of the weight of each connection according to current channel state [6].


Recently Zhu et al. proposed a dynamic security mechanism for real-time application on wireless networks [10]. Based on the system work load the security mechanism present will dynamically improve the security. The proposed algorithm is Improved Security–Aware Packet Scheduling algorithm (ISAPS); ISAPS is based on the system work load. ISAPS gives priority to schedulability rather than security. Under heavy load ISAPS increases schedulability by decreasing the security level of packets and under light load ISAPS strives to increase the security of each incoming packets. ISAPS is also based on the algorithm proposed by Qin et al. 2008, Security-aware Packet Scheduling (SPSS) algorithm [7].

When compared with SPSS, ISAPS have a better guarantee ratio, and a lower packet drop. Even though the packet drop is lower than that of SPSS, as packet arrival rate increases there is a constant increase in dropping of packets. So we propose Round robin based Secure-Aware Packet Scheduling (RSAPS) algorithm. RSAPS tries to improve the guarantee ratio and lower the packet dropping by giving equal chance of processing for each packet. RSAPS is based on the algorithm SPSS proposed by Qin et al. 2008 [7].

3. Packet scheduling model

3.1.Scheduler model

In our study we present a round robin based scheduler model compared with that given in [7]. Scheduling is done at an intermediate node, which will be placed in between a source and destination. This intermediate node will act as a transceiver. The packet scheduler is illustrated in Fig. 1. which depicts the scheduler model.

Newly arrived packets are put in the schedule queue to wait for the scheduling and assigned the highest security level. The real-time controller gets all the packets and sort according to earliest deadline first (EDF) policy. Then from the sorted list of packets ‘n’ number of packets will be selected for first time. Each packet in the round will have t time for its execution, after processing t time it will be switched to next. Once the total processing time of a packet is completed the packet will be replaced with new packet.

If the packet can be accepted the real-time controller will place the packet into the accepted queue. Real-time controller only considers the new packets in schedule queue, real-Real-time controller notifies the security-level controller to increase or decrease the security level of each packet. If a new packet cannot be accepted it will be rejected by the real-time controller and placed in the rejected queue. The security-level controller will decrease the security level of a packet to improve the schedulability.

Fig. 1. Scheduler Model

3.2. Packet Model


Table 1: Main notations used

Notation Definition

Pi The ith packet in packet set P

Ai The arrive time of pi

Di The deadline of pi

Fi The finish time of pi

Si The security level of pi

Ti The transmission time of pi

Soi The security overhead of pi

Pti The processing time of pi

Tpi Total processing time

Sti The start time of pi

Wti Waiting time of each packet in a single round

To calculate the security overhead of each packet the following equation can be used: Soi = Ti x (Si/ |S|) (1)

The total processing time Tpi can be calculated using the following equation can be used: Tpi =Pti+ Ti + Wti +Soi (2)

A packet will be accepted if the deadline of the packet is guaranteed, the packets accepted must satisfy the following property

Sti + Tpi ≤ Di Property 1 4. RSAPS Algorithm

RSAPS algorithm is a dynamic scheduling algorithm which will dynamically increase or decrease the security levels of packets based on the incoming load. RSAPS gives priority to schedulability rather than security.

RSAPS accepts packets based on property 1 i.e. the finish time of a packet must be less than or equal to the deadline of the packet. RSAPS is a heuristic algorithm. When a new packet arrives to the schedule queue it will be provided with maximum security level. Real-time controller present will sort the packets in the schedule queue based on earliest deadline first (EDF) policy. From the sorted packets ‘n’ number of packets will be selected by the round robin scheduler for scheduling. The time slice for each packet in round robin scheduler will be ‘t’ seconds. Upon finishing packet will be replaced with new packet. For a packet to be accepted the real-time controller will check whether the finish time of the packet is less than or equal to the deadline. Packets which meet this property will be accepted with maximum security.

If a new packet does not satisfy this property the real-time controller will notify the security level controller to degrade the security level of packet. Again property 1 is checked, this process goes on until the packet have reached a minimum security level. Even after reaching the minimum security level, still property 1 is not satisfied real-time controller will eventually drop the packet and place it on rejected queue.

In this algorithm the inputs include packet count, arrival rate, deadline and security level and the output will be scheduling decision.

5. Simulation evaluation

Simulation of this paper was performed using Microsoft Visual Studious 2010 with C# 4.0 and SQL 2008. The simulation environment consists of thirty source nodes and ten destination nodes and five intermediate nodes. Scheduling of the packets arriving from various source nodes is performed in the intermediate nodes once packet scheduling is done the intermediate nodes will forward the packet, packet scheduling reduces the packet dropping rate. In order to prove the superiority of our algorithm, we have compared our algorithm with the one proposed in [7] SPSS and the one proposed in [10] ISAPS.


Guarantee Ratio (GR) is defined as: GR = total number of packets accepted / total number of packets x 100% [10];

First we can evaluate our algorithm with previous algorithms based on guarantee ratio. Using the above equation guarantee ratio for each instance can be calculated.

Fig. 2, indicates the guarantee ratio of packets experienced at a range of 90 to 210. From fig 2 it is evident that at each instance our proposed algorithm will have a higher guarantee ratio than both SPSS and ISAPS. Even though guarantee ratio decrease as packet count increases it is always high than the other two algorithms.

Fig. 2. Comparison of Guarantee ratio

In the evaluation process we consider the number of packets dropped in each algorithm. Fig. 3. shows the comparison of dropping rate three algorithms for a number of packets at the range of 90 to 210. Graph indicates that RSAPS shows superiority over the other two algorithms. RSAPS is having the minimum number of packet drop in each instance.  


6. Conclusion

In this paper we present a Round robin based Secure-Aware Packet Scheduling algorithm RSAPS. RSAPS adaptively controls scheduling by increasing or decreasing the security level of packets based on the incoming work load. Under light load RSAPS provides packet with maximum security level and under heavy load RSASPS gives priority to scheduling by decreasing the security level of packet. The simulation results show RSAPS provides a higher guarantee ratio than the two prior algorithms SPSS and ISASPS. This proves that our algorithm is best suited for dynamic wireless network environment.


[1] Bjorn Hovland Borve, Packet Scheduling Algorithms for Wireless Networks, Norwegian University of Science and Technology. Department of Electronics and Telecommunications. 2008

[2] Hassan M, Landolsi T, Tarhuni M, A fair scheduling algorithm for video transmission over wireless packet networks, in: Proc. the IEEE/ACS Int’l Conf. Computer Systems and Applications (AICCSA 2008), Mar.–Apr. 2008, pp. 941–942.

[3] Jaspher W. Kathrine, Arun Raj, Packet Scheduling Algorithms in Different Wireless Networks A Survey, International Journal of Engineering Research & Technology (IJERT), Vol. 1 Issue 8, October - 2012

[4] Karygiannis T, Owens L, Wireless Network Security 802.11, Bluetooth and Handheld Devices, NIST Special Publication 800-48, Nov. 2002.

[5] Kensaku W, Shoji K, Yutaka T, Yoshinobu K, Eisaburo I, A packet scheduling algorithm for max-min fairness in multihop wireless LANs, Comput. Commun. 32 (2009) 1437–1444.

[6] Liu H, Wang Y, J. An, A novel SNR-based packet scheduling algorithm and compensation model for wireless networks, in: Proc. the 4th Int’l Conf. Wireless Communications, Networking and Mobile Computing (WiCOM 2008), Sept. 2008, pp. 1–4.

[7] Qin X, Alghamdi M, Nijim M, Zong Z, Bellam K, Ruan X, Manzanares A ,Improving security of real-time wireless networks through packet scheduling, IEEE Trans. Wireless Communication . 7 (9) (2008) 3273–3279.

[8] Qing Xiong, WeijiaJia, Chanle Wu, Packet Scheduling Using Bidirectional Concurrent Transmission in WiMAX Mesh Networks, School of Computer, Wuhan University, Wuhan, P. R. China.

[9] Sharifkhani A, Beaulieu NC, A mobile-sink-based packet transmission scheduling algorithm for dense wireless sensor networks, IEEE Trans. Veh. Tech. 58 (5) (2009) 2509–2518. 

[10] Xiaomin Zhu , HaoGuo, Shaoshuai Liang, Xiaoling Yang, An improved security-aware packet scheduling algorithm in real-time wireless networks, Science and Technology on Information Systems Engineering Laboratory, National University of Defense Technology, Changsha 410073, PR China.


Fig. 1. Scheduler Model
Fig. 1. Scheduler Model p.3
Fig. 2. Comparison of Guarantee ratio
Fig. 2. Comparison of Guarantee ratio p.5
Fig. 3. Comparison of packets dropped
Fig. 3. Comparison of packets dropped p.5