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DYNAMIC SWITCHING OF WPAN AND WLAN

发布时间:2017-03-05
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DYNAMIC SWITCHING OF WPAN AND WLAN

ABSTRACT: Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN) works under the unlicensed ISM band. Through the proposed dynamic switching mechanism based on vertical handover (VHO), the WLAN and WPAN interference is reduced and the throughput of the two systems is significantly improved at the expense of a small additional delay in the transfer of data traffic. VHO aims at providing service continuity and maximize throughput while limiting the so called “ping-pong effect”. The proposed algorithms can be applied either when WLAN and WPAN are able to exchange information as well as when they operate independently of one another. We propose two coexistence mechanisms based on the power level of the transmitted signal and packet traffic delay scheduling. It focuses on developing Simulink models for the coexistence of WLAN and WPAN protocols and the performance evaluation of these models.

Keywords-Bluetooth, Wi-Fi, IEEE 802.11b, IEEE802.11g, Coexistence, vertical handover.

  1. INTRODUCTION

Future trends in the wireless technology are to share and exchange data between the different wireless technology. The future devices can able to share the data over the same frequency range with the help of Vertical handover. The Vertical handover helps to achieve this by exchange of data between the different wireless technologies. So by using this we can use the best from the technology and we can explore more features such as power level reduction data rate increment and the increase in range of operation. The IEEE 802.15 working group is working on the development of interference issues of WPAN technology. They proposed two techniques to reduce interference caused by other technology operating in the same frequency band; these are collaborative coexistence mechanism and non-collaborative coexistence mechanisms. The collaborative coexistence mechanism helps in sharing the data between two different wireless nodes including WLAN and WPAN, where as the non-collaborative approach is unable to share data between the two wirelesses technologies like WLAN and WPAN. This paper is considering the approach of collaborative coexistence mechanism to share the data between the two wireless technologies. According to the IEEE 802.15 working group the sharing of data take place through the adaptive wireless medium access control mechanism, second approach is by using the packet transfer access, and third approach is by using the interference reduction mechanism.

The future trends in the mobile having equipped with the different forms of connectivity (mobile radio interfaces). Thus the power consumption of an mobile by these connectivity is an measure issue. If the systems are able to switch according to their need intelligently, then devices can utilise the maximum amount of power.

  1. WLAN

The IEEE 802.11b standard is a specification forWireless Local Area Networks (WLAN).Wi-Fi systems transmit data in the 2.4GHz ISM band. Data is transmitted on BPSK and QPSK constellations at 11Msps. A relatively large excess bandwidth (or bandwidth expansion factor) is used for the pulse-shaping filter,Wi-Fi products transmit at data rates up to 11Mbps. Typically, Wi-Fi devices operate atdistances up to 100 meters, range tend to change as per the conditions .

This technology based on CSMA/CA medium access with a positive MAC layer acknowledgement and a retransmission mechanism that aids noisy channel propagation condition and eventual undetected collisions. Today, WLAN standard defines high rate data throughputs; such as the IEEE 802.11b with a maximum throughput of 11Mbps and the IEEE 802.11g with maximum throughput of 54Mbps. Both IEEE 802.11b and 802.11g operate at the 2.4 GHz band. Typically, WLAN devices operate within 100 meters of distance range depending on the surrounding environment. While, the IEEE 802.11b utilizes direct sequence spread spectrum (DSSS) using complementary code keying (CCK) modulation, IEEE 802.11g is based on the orthogonal frequency division multiplexing (OFDM) modulation technique and the CCK modulation for backward compatibility with 802.11b.Wi-Fi has advantage of high data rate but at an expense of high power level. Data rate of a Wi-Fi technology increasing with advancement .Wi-Fi working on 1, 2 5.5,11 Mbps.

  1. WPAN

The IEEE 802.15 standard is a specification forWireless personal Area Networks (WPAN). Bluetooth is convenient low power radiofrequency connectivity for short-range communications. It can be used to replace the cables connecting Portable/fixed electronic devices build ad-hoc networks or provide data/voice access points.In the 2.4GHz ISM band, the use of spread spectrum is mandatory. Although DSSS can achieve higher data rate (11Mbps for 802.11b standard), FHSS has its advantage of low cost, low power, better security. FHSS also handles near-far problem better, since it will effectively block out-of-band signals. Considering the possible applications of Bluetooth, FHSS is a better solution.The hopping sequence is calculated using the master’s Bluetooth Device Address. It hops to every 1MHz channel with equal probability. Its 1600hops/sec fast hopping rateis enough to overcome slow fading in most indoor environment Bluetooth devices can communicate at ranges of up to 10 meters. Bluetooth devices do not need to be in direct sight of each other.This makes Bluetooth connectivity much more flexible and robust. The characteristics of Bluetooth technology low cost, low power, and radio based encouraged the concept of a personal area network (PAN). A PAN envelops the user in a small, mobile bubble of connectivity that is effortlessly available at any time. Bluetooth’s freedom from cables and potentialubiquity make it ideal for carrying your personal network around with you.

  1. VERTICAL HANDOVER APPROACH

In this approach of vertical handover, Bluetooth transmitter send data by using FHSS using GFSK modulation when the receiver sensitivity is minimum at that time transfer of data will not take place thus at that time approach of vertical handovercame to existence.For this approach of switching we are using Friis transmission equation which calculates the received power level as per the distance criteria. Bluetooth having operating range of 10 m so beyond the 10 m distance the power level required to receive by an transmitter is minimum at that time it will wait for 5 to 10 ms to check whether the connection is available or not .If after waiting also no signal received at the receiver at that time Wi-Fi network will start to work. Thus by using received signal strength we can estimate the available network.

Sensitivity is the ability of the receiver to sense the signal for the Bluetooth sensitivity is in the range of -50dbm (10pw). When the Bluetooth crosses the 10 m distance at that time receiver power is below the sensitivity of the Bluetooth receiver at that time the received power level can be used as the enabling signal for the Wi-Fi system.

If we set -50.001 dbm as a triggering signal to activate the Wi-Fi transceiver can switch from one network to another by using(RSSI).

RSSI (Received Signal Strength Indicator) is a more common name for the Signal value. It is the strength that one device is hearing another device. This value is measured in decibels from 0 (zero) to -120 (minus 120).The closer this value to 0 (zero), more potential in the signal.

Figure1: VHO proposed approach

In a Bluetooth network the basic network configuration called a piconet, consists of a maximum of eight devices and a transmission range of only 10 meters. The short range of Bluetooth arises frequent handoffs. When the Bluetooth device is connected with an AP, and moves out of range, after a small duration of time, the Bluetooth stack in the device declares the link to be dead and close the L2CAP connections. At this time the received power check mechanism came into picture which will check the power level which is set as threshold if the power level at the receiver is in that range so the switching of the network take place. So AWMA (ADAPTIVE WIRELESS MEDIUM ACCESS) and the mac layer will shift from the Bluetooth to Bluetooth link to Wi-Fi to Wi-Fi link

Receiver Signal Strength Indicator (RSSI) will help to reduce the power consumption. It compares the received signal power to upper and lower thresholds to see if it’s within the “golden range” and notifies the transmitter via LMP.Receiver will always give a feedback signal in the case of Bluetooth data transmission. Bluetooth also checks for the data transmission by using ARQ concept if data is not being transmitted at that time it will wait for a period and sends signal to transmitter to resend the signal same concept we can use for the power level check it will always check power level at particular distance and if the power level is very low which can be -50 dBm at that time20 dBm signal is required to enable an Wi-Fi transmitter.

Switching mechanism will work similar to the ARQ concept where the signal always checks for the confirmation of the signal. Feedback signal which is used for the confirmation of data received .In the similar way we use the RSSI signal received from the receiver which always correlate with the ARQ message signal if the data transmission is not there for some period of time at that time it will switch from one connectivity to an another connectivity.For switching from the Bluetooth low power signal to Wi-Fi signal with the high power level the receiver should send the enabling signal of high power level .so the high gain power amplifier should be used for the amplification of signal .

Figure2:-Device Constraints

Bluetooth and Wi-Fi operates at the different forms of modulation and spread spectrum technique. The spread spectrum technique used for the conservation of power level as well as for the protection of signal from detecting by other signal that is the Antigambling of the signal.Bluetooth uses the FHSS technique which is itself a secured form of communication scheme where the signal always hops on particular frequency and the receiver only knows when it is being paired with the transmitter device. Bluetooth transfers data at a rate of 1 MBPS which is at a power level of 1 mw (0dBm). When we compare this with the Wi-Fi this data rate and the power level then the comparative study shows that the Bluetooth is far better in compared with the power level but restricted with the distance issue and the data rate which is comparatively low .So if we consider the power issue and use it for the switching also then that will be advantageous so we can able to save the power level of the data at a particular distance.

The other mechanism which we consider for the switching purpose is the packet data switching .When we are sending the data on a particular channel then the channel always checks the data rate or the bandwidth of operation of the signal. When the data transmission is in the range of 1 MBPS then it will transmit the data by using a Bluetooth concept. Otherwise it will transmit the data by using Wi-Fi connectivity. By using this concept of switching mechanism we can save the power before starting the data transfer mode .If we combine this two mode of switching then we an able to save the power also and the data connectivity will be intelligent .When the user will move from Bluetooth to the Wi-FiThe Simulink model of the Bluetooth frequency hopping and the 802.11 b model used in this system .Where the transmitter will send the data firstly by using an Bluetooth concept and then it switches by using an friis equation .Power reduction is intended primarily to reduce the interference taking place with the other system which can enhance the system performance. The second main reason for the reduction in power level is to improve the system efficiency and power endurance of the device.

  1. RELATED WORK

Figure 3:- Simulink Model Integration of Vertical Handover

By using standard Simulink models

Simulation is done in Matlab /simulink environment where system uses the Bluetooth frequency hopping model and 802.11 b model of Wi-Fi.When we start the simulation then the Bluetooth will start to operate. Bluetooth master and slave(s). Two link types have been defined:

  • Synchronous Connection-Oriented (SCO) link
  • Asynchronous Connection Less (ACL) link

The SCO link is a point-to-point link between a master and a single slave in the Piconet. The master maintains the SCO link by using reserved slots at regular intervals.The Asynchronous Connection Less link is a point-to-multipoint link between the master and all the slaves participating on the Piconet. In the slots not reserved for the SCO link, the master can establish an ACL link on a per-slot basis to any slave, including the slave already engaged in a SCO link.

  1. SIMULATION RESULTS

Switching mechanism consider for the system usingfriis equation which we can implement in Simulink by simulating distance by using the formula of

Velocity for a normal human being is consider to be 0.125m/s . Gain of the transmitter and receiver is taken as 5 db transmit power of an class 3 Bluetooth using a power of 1 mw (0dbm).wavelength is varying from 2.4ghz to 2.483ghz.as per this the wavelength will vary from 0.125m to .120m.the switching mechanism is as shown below

Figure 4:-Simulink Model of Algorithmof Switching mechanism

Thus as distance increases the received power will go down and we have to consider the value at a distance of 10 m calculated from friis equation which is to be -50dbm.Thus the received spectrum with respect to distance is as shown below.The fig 5 representing the received spectrum of the receiver of Bluetooth and the received power which shows that the -25dbm is the received power which we can get at a distance of 1 m this power is sufficient for the data transfer.at this time of the data transfer the enabling of the Wi-Fi is not being required and the data transfer also being held.

Figure 5:-Simulink Model of Operational Bluetooth

At distance of 10M the power level of the Bluetooth receiver will go down which is shown in fig 6 .this shows that at a power level of -50dbm that is the -70dbW power the vertical handover is being possible. Thus the received power calculated from the Bluetooth RSSI signal is being used as an enabling signal and thus the Wi-Fi enabling signal will be send and the remaining data is being transferred by using an Wi-Fi which requires the power level of -20dBm.This power amplification take place by using an amplifier with gain of 70dbm or 40dBw.Thus the data which can be able to transfer by using an Bluetooth with an data rate of 1 MBPS is being transmitted.The power level required to transmit the data is also very less. So it will help to conserve the power and enhance the battery life of a mobile device.

Figure 6:-Simulink model of operational Wi-Fi

VII. CONCLUSION

In this paper the IEEE 802.11b and Bluetooth Frequency Hopping model in Math worksMatlab/Simulink has been provided. As a main result from simulations, Bluetooth frequency hopping model will provide an RSSI signal to the IEEE 802.11b standard when mandatory condition of vertical handover will come.

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The received power level will be responsible for the Wi Fito turn on .This will in turn helps to conserve the power of device as well as smaller interference to the IEEE 802.11b signal than Bluetooth 1 M bit/s data rate. Vertical handover scenario for the other connectivity’s can be considered for the future approach in which every connectivity be able to communicate by using a vertical handover scenario

References

[1] J.M. Peha, “Wireless Communications and Coexistence for Smart Environments,”IEEE Personal Communications Magazine”, pp. 66–68, October 2000

[2] TizianoInzerilli , Anna Maria Vegni “a reactive vertical handover approach for Wi-Fi-UMTS dual-mode terminals”Consumer Electronics, 2008. ISCE 2008. IEEE International Symposium

[3] Carla F. Chiasserini and Ramesh R. Rao ,“Coexistence mechanisms for interference mitigation between IEEE 802.11 wlansand bluetooth” IEEE INFOCOM 2002

[4] Jan Mikulka, StanislavHanus, “Bluetooth and IEEE 802.11b/gcoexistence simulation” Radio engineering, VOL. 17, NO. 3, SEPTEMBER 2008

[5] Roberto Cristi , “Wireless Communications with Matlab and Simulink: IEEE802.16 (WiMax) Physical Layer”

[6] JaniPuttonen*, Gabor Fekete*, JukkaMakela*, “Using link layer information for improving vertical handovers” 2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications

[7] KaoutharSethom, HossamAfifi ,“Requirements and adaptation solutions for transparent handover between wi-fi and Bluetooth” IEEE Communications Society 0-7803-8533-0/04/(c) 2004 IEEE

[8] HongfengWang ,“Overview of Bluetooth technology” July 3, 2001

[9] “Implementation of ieee 802.11p physical layer model in Simulink”Publication Database of the Vienna University of Technology

[10]Part 15.3: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPANs)

[11]A. M. Vegni, M. Carli, A. Neri, and G. Ragosa, “QoS-basedVertical Handover in IEEE 802.21 networks”, Proc. on Wireless Personal Multimedia Communication, WPMC 2007, Jaipur, India, 4-6 Dec. 2007.

Authors Bio:

Sagar Shriram Salwe received the Bachelor of Technology degrees in Electronics and Telecommunication from the Maharashtra Institute of Technology, Aurangabad, in 2010. He is pursuing Master of Technology in Radar & Communication from Defence Institute of Advanced Technology, Pune Maharashtra. His current areas of interest include Communication and radar applications.

Dr. K. Krishna Naik received graduation degree in Electronics & Communication Engineering from Sri Krishnadevaraya University, Anantapur in 2002, Post graduation from Indian Institute of Information Technology, Allahabad in 2004 and doctoral degree from Jawaharlal Nehru Technological University Anantapur, Anantapur in 2010. Currently he is working as an Assistant Professor in Electronics Engineering, Defence Institute of Advanced Technology, Pune. His current areas of interest include Electronic Warfare Applications, Software Defined Radio, Wireless Networks, Mobile Ad-Hoc Networks.

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