PERFORMANCE ISSUES AND ITS SOLUTIONS FOR MOBILE COMPUTING Narendra A. Patel* Lecturer, Mechanical Engineering U V Patel College of Engineering, Mehsana- Gujarat [email protected]

Savan K.Patel Lecturer, Acharya Motibhai Patel Institute of Computer Studies

Mehsana- Gujarat [email protected]

Pravesh.S. Patel Lecturer, Computer Engineering U V Patel College of Engineering Mehsana- Gujarat [email protected]

Abstract: Work from a non-fixed location using portable computing/communications devices such as laptops, notebooks, palmtops, smart cell phones and PDAs. Mobile Computing is very hot topic in the field of Information Technology now a days. But sometime it having some critical issues which are very important to solve for the unique performance of the mobile computer under considerable conditions. This paper include two basic problems and its solutions, which are generally found in the mobile networks. By providing this solution to the corresponding performance issues we can utilize optimum bandwidth of the mobile network under same situation as well as we can get flexibility to change the network without changing the physical configuration manually.

2. How Mobile Computer works? One possibility is to have a standalone computer capable of storing large amount of software and data files, processing power to support the required applications. Modern day laptop computer are something like this. Whenever you are static, connect to internet through an access point and you can do the file transfer, telnet, web browsing etc. While on the move, connectivity is desired for using software which requires cooperation of at least two machines

Key Words: Mobile Computing, Bandwidth Utilization, Portability, Physical address 1. Introduction: A computer which you can take with you all around. You can do all the things which can be done with a desktop computer. You should be able to use same software, which you use on a desktop computer The fundamental premise of mobile computing is that the information will be accessed from outside of the organization. As long as the information is within the four walls, the environment will be better known. It may be easier to control this environment and make it secure. When the information or computing environment is outside the controlled environment we do not have much control either from its users or usage patterns[7]. Today, all the computers of the world are interconnected through extranet. Moreover, in a majority of cases, mobile computing uses wireless networks. Wireless media works on the principle of broadcast; information is radiated to everyone within the radio wave range thus increasing the security threats. Unlike a physical attack, cyber attacks can be replicated quite easily. Therefore, unless special care is taken, all systems are open to

attack. This chapter discusses different techniques to secure information over mobile computing environment[2].

3. Advantages/ disadvantages • •

•

•

Very small, compact and light weight mobile computer Less power consumption and large battery life - this may not be true, if radio communication requires more power than to power up all necessary devices for a standalone computer on average basis. Higher reliability of data - theft of standalone computer means everything is lost. But here all information is stored on some static server.But data privacy while communicating to servers via the network has to be ensured. The performance highly dependent upon network and wireless channel conditions.[1]

4. Mobile Computing Issues Actual Mobile computer - somewhere in between the two extremes. • Issues due to • nature of medium • Mobility • Portability Disconnection • Common in radio environments - due to noise. • due to moving into dark areas • Blocking by servers e.g., due to too many requests to a file server. Standalone mobile computer can tolerate this kind of problem better. Portable terminals will not function Asynchronous operations - round trip latency and short disconnections can be taken care of. Synchronous remote procedure calls - After each request wait for response. Asynchronous remote procedure calls - After several requests have been sent then acknowledgement is asked for. Pre-fetching / lazy write back decouples communication from data usage/ generation. Decoupling allows the program to progress even during disconnection. In Distributed file system, users’ profile is used to keep best selection of files in the cache Whole files are cached instead of fixed block of data. 5. SOLUTION There is no way bandwidth can be increased, it can only be efficiently utilized. compression at the two ends of wireless link. Logging - since bulk usage more efficient than multiple small usage. Logging along with compression - still better – Larger block compress better[2]. The data communication bursty. The techniques for disconnection can also improve the performance in low bandwidth environment. During a burst demand temporarily exceeds the capacity burst is like short disconnection.

• Performance management The mobile host must discover an interface switch or a handoff and notify the correspondent host. Then both endpoints are aware that subsequent observed losses of the data in transit can be attributed to mobility rather than congestion. When the end-points are aware of mobility related activity, the sender marks the data that it is in its retransmit queue. A lost packet in this range triggers retransmission, but not the corresponding congestion control mechanism. Upon an interface switch, the sender resets the congestion window, slow start threshold, RTT, and RTO values, and proceeds to do a slow start as though it were initiating a new connection. Alternately, stable values from the previous cells can be used as hints. Same RTT values could be used in the new cell, and set the congestion window and the slow start threshold to half of congestion window’s old value to perform congestion avoidance. When IP endpoints at MH changes, the changing if its address is trapped by the kernel device control code [2]. All the sockets that use the affected interface are notified, and a switch detection routine is invoked. MH notifies the CH via an option field in the next MTCP packet. If operating on top of IPv6, MTCP can make use of IPv6 CH notification mechanism instead of using a special option.

6. Performance results[7] A non-fast-retransmit trial used to baseline strict TCP performance under Linux 1.3.71. Compare fast re-transmitting TCP to MTCP in a LAN environment. Introduce 100ms delay, to simulate long-haul networks such as satellite WANs. Isolate the impacts of fast re-transmits in Linux 2.0.31. Effect of failing to perform a slow-start on the network. 6.1 Performance results: trial 1 Test interface from 10Mbps Ethernet to SLIP using low-bandwidth utility. Interface switch is detected only once re-transmission has been initiated by an RTO timeout. Packet capture: # transmitted versus time. Each tick mark on graph represents a single packet transmitted from mobile client to the fixed server. Gaps – periods of silence. Two tick marks with same sequence number – re-transmission.

Low bandwidth interface switch without fast retransmits

6.2 Performance results: trial 2[7] MTCP versus standard TCP when network delay is present. Both perform similarly. Both protocols recover in 200ms; MTCP’s slow start begins earlier.

Performance of TCP vs MTCP with small network delay

.

7. Case Studies UPS Parcel Delivery Tracking Application [5] When Fedex introduced a wireless network application to keep track of document and parcel shipments, UPS was pressured to respond with a similar or better service. The result was the introduction in February 1993 of a nationwide cellular-based wireless data service. This was the start of a major exploitation of wireless, Internet and supporting technologies to achieve a competitive advantage as well as to improve worker productivity Pre-1996Implementation

Through cellular technology and a broad alliance of more than 70 cellular carriers, package-delivery information is transmitted from the company’s 50,000 vehicles to the UPS mainframe repository in Mahway, NJ, thus enabling UPS to provide same-day package-tracking information for all air and ground packages. Previously, this information was not available until the next day after delivery. With its delivery information acquisition device (or DIAD, a custom-built electronic data collector), UPS is currently the only carrier able to capture both delivery information and customers’ signatures. This data is then entered into the cellular network through Motorola-supplied cellular telephone modems. The cellular network provides the connection between UPS vehicles and UPSnet, UPS’ private telecommunications network. These systems are set up to be fail-safe, with cellular redundancies, dual access to UPSnet, and multiple connections to the data system. Competitive Business Advantages and Benefits

UPS believes that their circuit-switched cellular data network service is the most comprehensive radio system available today. It covers a greater area and is more reliable than other mobile radio network alternatives. Key customer benefits quoted by UPS include: Immediate access to delivery information on more than five million UPS packages daily. The most extensive geographic coverage of any mobile communication alternative. (More customer shipments can be given real-time information on delivery status.).A high degree of reliability as a result of the service’s redundancies and backup systems. Flexibility to accept future network technologies. How UPS’ Delivery Status Application Works

The DIAD is inserted into a DIAD vehicle adapter (or DVA, which looks like a notebook computer docking station). The DVA in turn is connected to

a cellular telephone modem (CTM) that transmits information from the UPS vehicle to the cell sites, where it is routed through the carrier’s cellular switch and special primary access equipment. This equipment directly connects to a UPSnet packet switch, which transmits the information to the UPS mainframe in Mahwah, NJ. Once the information is incorporated into the delivery-status database, it is available to the company’s customer service representatives. UPS Delivery Information Acquisition Device (DIAD)

The DIAD is a hand-held electronic data collector that UPS drivers use to record, store, and transmit information, thereby helping UPS to keep track of packages and gather delivery information. A linchpin in UPS’ nationwide, mobile cellular network, the DIAD digitally captures customer signatures and package information — an industry first. This capability enables UPS to keep accurate, paperless delivery records. Drivers insert the DIAD into a module in their delivery vehicles to transmit information over UPS’ nationwide cellular network for immediate customer use. Key Features of DIAD

• Contains 1.5 megabytes of RAM - old, not 1999 DIAD III • Consolidates multiple functions into single keys — saves time and space • Digital signature-capture is an industry first • Built-in acoustical modem; if a driver cannot access the vehicle, data can be transmitted via telephone • Built-in laser scanner reads package labels quickly and accurately • "Smart" software knows driver’s next street • Interacts with UPS cellular service Both DIAD and DVA were custom built for UPS by Motorola. Southwestern Bell, GTE and PacTel all played key roles in putting together the cellular network consortium of more than 70 carriers. 1999 Update to UPS Infrastructure:

UPS has replaced its DIAD hardware to DIAD III again manufactured by Motorola and are now employing Motient network - transit time for dispatch of information in real time has been reduced significantly. Project

Costs

and

Benefits

UPS has estimated the total cost of the project at around $150 million. Senior executives point out that the resulting increase in market share let alone retention of the company’s competitive edge

completely justifies the investment. In addition to the business imperative, UPS cites the following benefits from the application: • Higher productivity of operational staff resulting from the revamping of processes and reductions in parcel-handling times. • Improved accuracy; elimination of illegible handwritten records • Speedier package delivery and tracking • More information available for customer verification of package delivery and receipt

required for transportation companies, not for parcel delivery companies. If this is a serious requirement, consider hybrid networks - contact Motient.

8. References: 1. Dr. Yatindra Nath Singh, EE/ACES, IIT Kanpur “Mobile Computing Networks “ 2 Vassilis Tsaoussidis, Ibrahim Matta , Boston ,” Open Issues on TCP for Mobile Computing”

Unique Features of UPS Application

The UPS project is characterized by the following features: • A unique implementation of analog circuitswitched cellular networks that meets UPS’ wireless and OLTP file transfer application designs. (The customer service inquiry application is based on wired networks.) • The business justification for implementation was based on a perceived need to maintain a competitive advantage, rather than on economic considerations. • The complete reengineering of package-handling business processes. • A unique ability to capture signatures on handheld, pen-based custom computers. • Huge backend legacy systems (primarily IBM) 15 mainframes with over 16,000 MIPS processing power and 149 terabytes of Database store - considered world's largest IBM Db2 installation. Lessons from UPS & Fedex Projects for Courier Industry (Source - Editors of MobileInfo Site) As mobile computing consultants, we would like to suggest the following points to other organizations investigating similar solutions: • Most courier companies including small ones can benefit significantly from mobile computing solutions with positive ROI in 2 to 3 years. Question you should ask is not if but when, what type of harware and network solution and how to implement. • You need not (and should not, unless you are that big) utilize custom hardware. There is off-theshelf hardware available now to serve most functional needs. • CDPD, American Mobile's Motient, Bell South Wireless Data offer attractive wireless networking solutions. Satellite coverage is

3. Syed A. Ahson and Imad Mahgoub - Boca Raton, Florida, “Research Issues In Mobile Computing” 4. Wireless and Mobile Computing , prepaid by first consulting group. October 2001 5. http://www.mobileinfo.com/ 6. Prasun Dewan , North Carolina ,”Replication for Mobile Computing” 7 Sirisha R. Medidi, WSU, “TCP Performance in Mobile Computing Environments”.