The convergence of voice and data networks in the business environment takes a new dimension with the emergence of wireless networks. The freedom of mobility offered to users in a wireless LAN has proven to give a significant boost in productivity and efficiency. morale. This is the strength of work related to their office when the work. Workers can access company files and receive important communications from anywhere on the corporate campus that is within range of a wireless access point. With voice communications thrown into the mix, mobile users can stay connected while traveling within the property or outside, even on the road. Acceptance of the concept of converged fixed mobile telecommunications industry that promises to fuel the fire for the adoption of VoIP over WiFi. The challenges of implementing VoIP over WiFi networks As with any emerging technology, there are challenges to overcome. The development of the converged network, i. e. voice and data over the same LAN IP core, while still a norm, be beneficial for businesses both in terms of cost and productivity. Add the prospect of VoIP on a wireless network provides a set of new questions. VoIP technology is a sensitive time. Appeals must be established and authenticated, and the voice packets must arrive at their destination without interruption and on time. This requires an almost continuous network stream, without interruption by the less sensitive data transmissions. Implementing Quality of Service (QoS) techniques for wired LANs ensure that voice packets have priority, and call quality issues such as latency, jitter and packet loss have been sufficiently taken into account. Enter the standards based wireless network, a technology at an early stage of development, and other challenges arise. While the cable network today offers many bandwidth for voice and data coexist, WLANs provide less bandwidth, and quality of service must be revisited. Security measures such as authentication and encryption must be implemented and can exacerbate the problem by increasing the size of the package of voice. In addition, users on the move crosses access points wireless where handoffs must be fast and smooth. The IEEE 802 standards governing wireless technology are evolving rapidly and promise to meet a wide range of issues WiFi. The increase in available bandwidth, packet prioritization for voice QoS, authentication protocols and encryption for security and improved techniques for homelessness are addressed. Also in development is the wireless technology known as WiMax, which provides the implementation of broadband wireless communications over distances up to 30 miles. The evolution of WiMax could be of great importance for developing countries, as well as the local metropolitan networks. Security in a VoIP / WiFi network Companies wishing to implement wVoIP must consider security issues at the outset. As with any IP network, the dangers of hacking, denial of service diversions and spam, all hiding in the shadows. Because a wireless network uses radio frequency as the transmission media, security normally provided by a firewall from a wired network is not enough, simply because of physics. Considering that, for breaking into a wired LAN requires hacking is physically inside the network or to hack through the Internet, WLAN, they can seize the transmission network of air while was parked in the street. The security issues that network managers must consider in a VoWLAN are intimate conversations, and protection of the network infrastructure. For wireless networks, security has been a rocky start with the implementation of WEP as a security mechanism. WEP for authentication and encryption between the user and the access point, and was found to be easily hacked. The 802. 11i standard, adopted as WPA2 (Wireless Protected Access) provides robust security for the most demanding two-way authentication between the user and the network, and uses AES (Advanced Encryption Standard) as a cipher. As network operators plan to deploy a wireless VoIP, the biggest security threat they face is the incorrect implementation. Improving safety in the design of the initial deployment can and should affect the network topology, and material costs. Failure to do so could lead to additional costs in the loss of services and revised in the event of network compromise. WiFi, VoIP and cellular networks Manufacturers of cell phones are radios in their wireless handsets to ever increasing rate. New versions of mobile operating systems come with a built in VoIP stack, inviting carriers and manufacturers to add VoIP capabilities to their devices. Double and quad band cell phones can choose between the strongest network available, cellular or WiFi, and make a call accordingly. As mobile phones become more like mobile offices, the advantages of a mobile workforce has emerged. In the case of road warrior, the ability to communicate by email, text messaging, video or voice, allowing them to stay on the road longer without losing touch. In an era of instant information, applications, mobile office allows files to be downloaded, edited and uploaded by increasing the productivity of the traveler at the point where almost anything can be done in the office can be done on road. A cell phone that can switch between cellular networks and Wi-Fi can significantly reduce telecommunications costs at headquarters. With WiFi hotspots flourish in hotels, cafes, and local area networks around the world, mobile workers can stay in touch with the office and the family both on and off the job. With the addition of a VoIP service provider, cheaper VoIP calls can be made from any WiFi network at the touch of a button. Imagine, if you want a future where a telephone, a phone number, seamlessly browse the cellular networks, WiFi networks, cable and fixed line PSTN. When roaming and switching between disparate networks occur without interruption or loss of call quality. Fixed to mobile convergence is the watchword of the decade, and the IP Multimedia Subsystem (IMS) architecture is the mechanism that promises to bring us to arrive. The aim of IMS is to provide all services and applications that the Internet provides, both current and yet unimaginable. IP services such as VoIP, push to talk cellular text messaging (POC), videoconferencing, community services, presence information and file sharing are just some of the possibilities. Designed to work with any fixed, mobile or wireless packet switched network, backward compatibility for circuit-switched legacy phone system is ensured by the use of gateways. Although still in its infancy, IMS is already implemented by AT & T as the platform in its newly acquired cellular network Cingular. Interest in investing in new infrastructure for fixed and mobile operators has been up and down, as they weigh the costs and benefits of new technology. As the technology of VoIP over WiFi networks continues to grow, companies of all sizes can reap the benefits of increased mobility, productivity and significant cost savings. standards committees are constantly working on ways to improve safety and quality of service and fixed-mobile convergence gains acceptance in the telecommunications sector, more choices in services and applications to IP available to companies will surely follow. What is also interesting to look at is how these very intensive applications the bandwidth will be determined by carrier networks, and how it will affect the neutrality of the Internet.