Chapter 1 Overview

Recommendations for Successful VoIP Surveys

Figure 1-1 ACU Site Survey Window

Noise is defined as a 2.4-GHz signal that is not in an 802.11 DSSS format but is in the frequency range of the access point’s configured channel. The noise can originate from an 802.11 2.4-GHz frequency-hopping radio, a 2.4-GHz wireless phone, a 2.4-GHz HAM radio, a Microwave oven, or a Bluetooth radio. Signals from a distant out-of-network 802.11b or 802.11g radio may also be seen as noise. Any 2.4-GHz signal that the access point cannot decode is considered noise. However, valid data packets from 802.11b or 802.11g radios that are not associated to the access point are considered data traffic. Those packets are decoded by the access point and client devices but are discarded. However, they increase the channel utilization on the access point, thus limiting the number of voice clients that can associate. Same-channel interference must be minimized.

If the signal strength on a valid packet is higher than the receiver threshold of the access point radio or the client device radio, the data packet is decoded. Most 802.11 radios have a receiver sensitivity value of –94 dBm to –85 dBm at a data rate of 1 Mbps (the lower the dBm value, the better the radio’s receiver sensitivity). Radio receiver sensitivity changes with data rates; for example, an access point radio might have a receiver sensitivity of –94 dBm at 1 Mbps, but the radio sensitivity might be –84 dBm at 11 Mbps.

The access point discards random data traffic--valid packets that can be decoded but which are not from clients associated to the access point. Random data traffic can originate from a shared media or from a client device that is transmitting at a data rate that the access point does not support.

In Figure 1-1, the noise level reported by the ACU is –92 dBm and the PCM350 receiver sensitivity at 11 Mbps is –84 dBm, which provides a margin of 8 dB at the receiver. A signal strength value of –48 dBm less the noise value of –92 dBm equals an SNR of 44 dB as reported by the ACU (see Figure 1-2).

Site Survey Guide for Deploying Cisco 7920 IP Phones

 

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Cisco Systems 7920 manual ACU Site Survey Window
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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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