Cisco Systems 7920 IP manual VoIP QoS, Rssi

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remember that the Cisco 7920 has somewhat different roaming characteristics than Cisco Aironet Network Interface Cards (NICs). This includes thresholds on the Cisco 7920 that determine when the phone roams or how much the RF environment needs to change in order to determine when a roaming event should occur. Because of this, it is recommended that a secondary site survey be performed for the Cisco 7920s. This gives you the opportunity to tune the APs to ensure that the Cisco 7920s have enough RF coverage and bandwidth to provide proper voice quality.

The design recommendation is that the Received Signal Strength Indication (RSSI) level in the RF network is at least 20 throughout the network. This provides the Cisco 7920 with the minimum signal coverage to be able to not only initiate a new call, but also roam properly between APs.

RSSI

dBm

15

30

45

60

−85

−70

−50

−35

The design recommendation is that the QoS Basis Service Set (QBSS) level on the APs is kept lower than 40. If the Cisco 7920 attempts to initiate a call and the QBSS element in the beacon is more than 40, the call will fail with a ￿network busy￿ tone to the user.

The power levels of the APs vary from network to network and need to be adjusted to meet site−specific requirements. On the APs, the coverage area increases as the power levels increase. But this does not necessarily mean that all the APs should be set to 50 or 100mW. This could potentially create an RF environment where the Cisco 7920s roam too frequently because of RF coverage overlap. Frequent roams could potentially cause interruptions in the overall voice quality. On the Cisco 7920, another tradeoff to consider is that the higher the power−level, the shorter the battery life.

VoIP QoS

While Voice over IP (VoIP) does convert voice signals into IP data packets and converge them with data traffic, the requirements of voice and data are very different when transmitted over an IP network. Data traffic can be classified with the following characteristics:

∙Bursty ￿ Traffic can be sent in large or small bursts, depending on the application.

∙Bandwidth ￿Greedy￿ ￿ Transmission Control Protocol (TCP) applications attempt to use as much bandwidth as the network allows.

∙Packet Loss Insensitive ￿ The retransmission capabilities of TCP allow data to continue to work correctly even with packet loss on the network.

∙Delay Insensitive ￿ Most TCP applications can handle some packet delay without effecting overall performance.

Cisco − Wireless IPT Design Guide for the Cisco 7920 IP Phone

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Contents Table of Contents Prerequisites IntroductionRequirements Cisco 7920 IP Phone Overview Wlan OverviewRF Overview Site Surveys and Design Recommendations Components UsedVoIP QoS Rssi∙ Delay Variation Jitter Not to exceed 30ms Security for the Cisco 7920 and Wlan Networks Number of 802.11b Devices per AP Network SizingNumber of 802.11b IP Phones per AP Page Numbers of 802.11b Phones per Layer 2 Subnet or Vlan Understanding Layer 2 and Layer 3 Roaming Understanding Roaming TerminologyLayer 2 Roaming Page Layer 3 Roaming VLANs Wlan QoS for VoIP Page Page Page Interconnecting WLANs to Cisco Campus Infrastructure Connecting APs to the Catalyst 3550 SMI or EMI Connecting APs to the Catalyst 2950 EI Connecting APs to the Catalyst 2950 SICaveats and Limitations Designing Around the Lack of Layer 3 Roaming Call Admission ControlOther Caveats and Limitations Related Information

7920 IP specifications

The Cisco Systems 7920 IP phone represents a significant advancement in wireless communication technology, designed specifically for enterprises that require mobility and efficiency in their communication systems. This versatile device integrates seamlessly into a Cisco IP telephony network, allowing users to maintain connectivity while on the move, which is essential in fast-paced business environments.

One of the key features of the Cisco 7920 is its robust wireless capabilities. Operating on the IEEE 802.11b/g Wi-Fi standards, it provides a reliable connection to corporate networks, ensuring that users can access voice, data, and video services without being tethered to a desk. The phone supports dynamic call handling and features a responsive LCD display that enhances user interaction, making it easier to navigate menus and manage calls.

The Cisco 7920 also offers exceptional sound quality, thanks to its advanced audio technology. With Wideband audio support, users can experience clarity in conversations, which is particularly important in environments where clear communication is vital. The phone is equipped with noise-canceling capabilities that reduce background noise, allowing users to focus on their conversations without distractions.

Security is another critical aspect of the Cisco 7920. The device supports several security protocols, including WPA and WPA2, ensuring that all communications are encrypted and secure. This is crucial for organizations that handle sensitive information and need to comply with industry regulations.

Additionally, the Cisco 7920 features an extended battery life, enabling users to make calls throughout the day without frequent recharging. Its lightweight design and ergonomic build make it comfortable to use for extended periods.

In terms of integration, the Cisco 7920 IP phone is compatible with various Cisco Unified Communications Manager software versions, allowing for easy configuration and management within existing network infrastructures. Its support for multiple languages also makes it a suitable choice for international organizations, accommodating diverse user groups.

Overall, the Cisco Systems 7920 IP phone combines the necessary features, technologies, and characteristics to meet the demands of modern enterprise communication. Its blend of wireless capability, superior audio quality, security measures, and integration versatility makes it an excellent choice for organizations seeking efficient and reliable communication solutions.
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