Chapter 1 Overview

Recommendations for Successful VoIP Surveys

degradation. This quality requirement also dictates the need for a fast roaming solution between access points where the network can reassociate a client to a new access point within 100 ms (that is, without suffering at most one packet delay or loss). People often walk around while talking on the phone, so users making voice calls tend to roam more than users of wireless computers. Users of wireless computers roam, but because very few users walk and use their computers at the same time, computer users are not using their computers when the roam occurs.

Because it might not be possible to have a VoIP network and WLAN network in place before the WIPT site survey, this document also describes a WIPT site survey process using standard wireless client cards and utilities.

Cisco recommends that all WIPT site surveys use diversity enabled access points and diversity antennas because a diversity configuration provides better throughput performance. A simple throughput test using an FTP data transfer of 50 MB in an office environment (with low multi-path signals) shows a 3-second improvement when using a diversity configuration. Diversity configurations are especially important in environments such as shop floors and hospitals, which often have heavy multi-path signals.

Cisco also recommends that you use 256-byte packets when you perform receive and transmit tests during the survey. Voice traffic consists of two-way transmissions, usually a burst of packets in one direction followed by a burst of packets in the other direction. You should check performance, error rates, and signal levels in both directions.

This document also describes how to use signal levels and signal-to-noise ratios (SNRs) in WIPT site surveys. WLAN site surveys that use only signal level tests are designed to identify the wireless network coverage area. Previous site surveys have shown that signal level tests alone are not sufficient for voice traffic and many times are not sufficient for data traffic. WIPT site surveys must also consider voice call capacity within a wireless cell. Currently, call loading is 7 active voice calls per channel using the G711 codec. This number is based on simultaneous requirements for data clients and quality voice calls with current data rates and packet sizes. Cisco recommends that all WIPT site surveys and installations use non-overlapping channels. For 802.11b/g operation the non-overlapping channels are a minimum of 5 radio channels apart. Cisco also recommends that you use a data rate of 11 Mbps to determine the cell size for the Cisco 7920 WIPT handset. If other data rates are allowed, call capacity might be substantially lower.

Getting started

Part of any site survey is measuring the noise level within a wireless cell. Noise levels vary from site to site and also within different locations of a site. The noise level affects a radio’s ability to receive data or voice packets. Figure 1-1uses the Cisco Aironet Client Utility (ACU) and a Cisco PCM350 client adapter to identify the noise level, signal strength, and SNR at a specific location with a wireless cell. The ACU window shows that the signal strength is –48 dBm, the noise level is –92 dBm, and the SNR is 44 dB.

Site Survey Guide for Deploying Cisco 7920 IP Phones

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Cisco Systems 7920 manual Getting started
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7920 specifications

Cisco Systems, a leading player in the global networking and communications technology sector, designed the Cisco 7920 Wireless IP Phone for mobile professionals seeking seamless connectivity in various environments. Primarily aimed at enhancing communication within enterprise settings, this wireless device offers a plethora of features that cater to the specific needs of businesses.

At the core of the Cisco 7920 is its robust wireless functionality. It operates on IEEE 802.11b/g wireless protocols, allowing users to connect effortlessly to Wi-Fi networks. This flexibility enables employees to communicate effectively from various locations within an office space, promoting mobility and collaboration without being tethered to a desk.

The ergonomic design of the Cisco 7920 prioritizes user comfort. Its lightweight casing and intuitive button layout ensure that users can navigate the interface with ease. The device is equipped with a vibrant color display, allowing for clear visibility of caller ID, call status, and menu options, enhancing the user experience further. Additionally, the handset supports a wide variety of languages, making it suitable for global teams.

In terms of features, the Cisco 7920 is loaded with advanced capabilities. It supports voice over IP (VoIP), delivering high-quality audio and ensuring reliable communication. Users benefit from features like a contextual menu, call hold, transfer, conference calling, and voicemail access on the go. The phone also offers a wide range of ringtones, allowing customization to suit personal preferences or company branding.

Security is a crucial aspect of modern telecommunications, and the Cisco 7920 does not fall short. It incorporates industry-standard security protocols such as Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA), safeguarding communications from potential threats.

Moreover, the Cisco 7920 integrates seamlessly with Cisco Unified Communications Manager, enabling centralized management and control. This integration ensures that IT departments can deploy, manage, and troubleshoot devices efficiently, streamlining operations while ensuring optimal performance.

In conclusion, the Cisco 7920 Wireless IP Phone stands out as a versatile communication tool designed for the fast-paced workplace. Its combination of wireless connectivity, ergonomic design, advanced features, and robust security makes it an essential accessory for businesses looking to elevate their communication strategies. With its established reputation, Cisco continues to support companies in achieving seamless connectivity and effective collaboration.
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