Since the Voice-Over Internet protocol (VoIP) evolution was introduced to this generation technology, the mobile communication can be improving and shaping the effective costs.  The improvement of technology would enhance the capability of dual-mode cell phone handsets in Wi-Fi (802.11b) and GSM; the dual-mode handset is a mobile phone that can handle both techniques in sending and receiving data and voice.  And particular dual-mode Wi-Fi and GSM handset is mainly about cellular and broadband Wi-Fi networks.  Recently the combination of dual-mode Wi-Fi and GSM handsets have been every popular in the mobile communication industries.  The ultimate goals of this converged network are simply low costs and alter the absence of cellular networks.  Therefore, it has been popular in deploying the Wi-Fi (802.11b) network to the public and private locations around the world.  In recent studies show the sale of dual-mode handsets have exceed over hundred million devices in 2008.  These studies would prove the mobile communication can be altered the cellular technologies into the Wi-Fi VoIP environment.  Perhaps, cellular phone can roam around the globe freely likes a broadband cordless phone without additional costs.  Although, the effective costs have been dual-mode handset benefit, and what is about subscribers’ convenience?  In this research paper will present the dual-mode Wi-Fi and GSM handset and its application along with Unlicensed Mobile Access networks. In fact, this paper also discusses the issue of dual-mode and handset devices like Nokia 9500 Communicator, Motorola MPx, and D-Link’s V-CLICK.

        The Wi-Fi is an IEEE 802.11b; a simple wireless network likes radio technology.  Today, this type of network is very popular in telecommunication simply low cost.  And especially the absence of cellular network in certain airspace area such as hospitals, government, hotels, airports, and etc; therefore, the wireless IEEE 802.11b plays an important role in mobile communication.  The introduction to dual-mode cell phone with capability of voice-over-wireless network or better known as (VoIP) has certain ultimate goals in mobile communication.  In the recent years, the voice-over Wi-Fi software and hardware development have implemented the mobile communication.  This factor promotes a huge market benefit in deploying five hundred million cellular handsets to the market.  According to Phil Solis, a Senior Wi-Fi Analyst at ABI Research says, “Many enterprises now have established Wi-Fi networks and integrating voice-over-Wi-Fi functionality is a natural progression.  As Wi-Fi network proliferate, it only makes sense to give users the ability to switch from a cellular carrier’s network to the enterprise Wi-Fi network.”  The improvement of technology tailors the way of operating telecommunication with several factors.  The first factor is coming to the reduction costs secure the high performance services.  Secondly, network has improved yearly in upgrading the enhanced voice and data services to the cellular phone.  This factor includes the 3G data network, which was introduced to the mobile communication in the past five years.  Third factor is the augmentation of Wi-Fi technology to where is lacking cellular coverage.  For example, certain building in the urban area location cellular networks from towers are blocked by airspace.  Therefore, the Wi-Fi technology would provide more benefits through broadband networks.  Fourth factor is resources and bandwidth; a typical voice channel takes only 64 kilobit per second, and with the modern broadband network can provide plenty of voice channels.  The final factor is the telephony communication evolution from using the SIP-based signaling protocol, which known as Internet Protocol Multimedia Subsystems or IMS (for short).  The usage is simple and easy in handing-offs cellular and Wi-Fi infrastructure.

       The Unlicensed Mobile Access is a convergence network by using Wi-Fi standard network.  According to UMA Architecture define it as, “an extension of GSM/GPRS mobile service into the customer’s premises that is achieved by tunneling certain GSM/GPRS protocols between the customer’s premises and the Core Network over a broadband IP network, and replaying them through an unlicensed radio link inside the customer’s premises.”  The network delivers low cost with high performance in mobile communication at the office and public wireless network.  There are certain companies provide the low-cost UMA deployment likes T-Mobile IPAccess and HotSpot.  T-Mobile provides over millions HotSpot and IP Access at the Airliners lounges, private sectors, public sectors, Starbuck stores, and the mall kiosks within the United States.  The company also introduces T-Mobile at Home services, which the subscribers can use their broadband networks and SIM (Subscriber Identify Module) card to make the calls.  There are millions growth of mobile communication substitution in yearly, but the performance in maintaining the network is very challenges in delivering the services. The dual-mode Wi-Fi and GSM handset can be accessed through the Unlicensed Mobile Access router network.  Most of these devices are available usage at the home, company office, local libraries, and even convenient public places like shopping malls, airports, and hospitals.  With the Universal Mobile Access network, the operators and subscribers would save lot of money in operating and communicating.  Especially it is very convenient for the subscribers, which they could use their mobile services at anytime and anywhere within the operated locations.  The way of Universal Mobile Access work is starting from the mobile provider through their Mobile Core Network such as circuit packet, IMS services, and etc.  The UMA Network Controller (UNC) delivers these services over the broadband networks, and manages mobile services as well as the mobility access between works. The UMA Enabled Femtocells device can provide the UMT and GSM networks that work for most of the standard mobile cellular phone.  From there, cellular phone can access through the UMA device to the Mobile Core Network through VoIP.

          What are the issues that dual-mode Wi-Fi and GSM handset involve, and how these involvements become realities?  The most complicated one is the handoff situation between two networks; in particularly the problem with existed signaling while the device is in-used.  For example, a subscriber is GSM network for having a conversation with someone; however, the call must be interrupted before switching to the Wi-Fi network.  Perhaps, it is not allowing switchover while the call is in progress, unless the call is terminated due to no reception from the GSM network.  The second complication is the billing system; especially the Wi-Fi network is cheaper but not one hundred percents free.  Maybe, customers must subscribe for both networks in their service package plan, so it is more convenient for both subscriber and operator.  Other issues are the phone integration, device power management, and codec usage.  The phone can stay on the GSM network with the device on sleeping mode; however, in contrast Wi-Fi requires the phone to be on in order to scan for signaling.  Sometimes calls are affected by the latency and packet loss.

        When comes to dual-mode Wi-Fi and GSM handset devices, the mobile communication companies fears to lose their revenue due to low-cost in the Wi-Fi network.  Today there are many technology companies produce cellular phone with embed Wi-Fi capabilities.  According to Phil Solis, “but long term, as with most new developments, carriers will likely see dual mode cellular / voice-over-Wi-Fi handsets as a means to differentiate their offerings.”  The mobile communication companies have to accept the realities of changing the way of communication.  Therefore, T-Mobile was the first carrier to provide easy ways to communicate between cellular and Wi-Fi networks by using the same device.  So, what are the devices have capability to handle both Wi-Fi and GSM network out in the current market?  There are devices such as Nokia 9500 Communicator, Motorola MPx, HP 6300 Series, D-Link’s V-Click, and etc.  These handset devices are operated by Microsoft Windows Mobile, Symbian, Blackberry, and etc.

       The Nokia 9500 Communicator has capability to handle Wi-Fi, GSM/GPRS and EDGE networks.  It integrates with Wi-Fi 802.11b, which has the abilities to support 64 and 128 bit WEP data encryption.  It uses the latest Symbian operating system that is usually for the Smartphone.  It displays a high revolution graphic in color, and has large keyboard for text messaging.  The user can customize the setting such as profile, ringtones, speed dials, and much more in this application.  The calendar, personal contacts, message and personal folder are also including in the handset application.  Furthermore, the handset also supports SMTP, IMP4, and POP3 mail protocols; which user can have multiple email accounts in one devices.  

          The Motorola MPx is built similar to the Nokia 9500 Communicator, but the handset has unique QWERTY keyboard.  It has the tri-band services are built in the device such as capabilities to handle infrared, Bluetooth 1.1, IEE 802.11b, GSM 900, GSM 1800, GSM 1900, and GPRS networks.  The applications are including Pocket Outlook, MSN Messenger, Pocket Internet Explorer, Windows Media Player, Voice Recorder, Calculator, Calendar, Terminal Services, Excel, Word, and etc.  It able to handle 200 MHz, and has the Secured Digital and MMC memory expansion slot. 

       The D-Link’s V-CLICK phone has the dual-mode Wi-Fi and GSM capacity.  The company released the handset into the market in 2009 with full features like tri-band GSM.  Also, has the ability to handle Wi-Fi 802.11b with a speed of 2.4 GHz access.  The handset phone book is operated from the Subscriber Identification Module card.  The handset is built with a click of button can switch from cellular mode to Wi-Fi mode; however, the user must configure the wireless SIP profile.  This handset has strong security such as WEP, WPA, and WPA2 for data and voice encryptions.

         In brief, the dual-mode Wi-Fi and GSM networks availability would enhance the mobile communication network to the next generation.  The Unlicensed Mobile Access is getting more popular because of low-cost service with minimal maintenance.  The dual-mode issues are complicated; however, they will not stop in populating new services.  Due to improvement of technology yearly, the dual-mode handset device is getting more affordable to the customers.  With capabilities of new application features, the device can handle most of the user’s task and security to the high standard. 

References

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