Recommended Data Rate for Optimal VoWLAN Design

B.

In a predictive site survey, an engineer uses a software tool to simulate the wireless network coverage and performance based on the building's layout, materials, and other factors. The goal of the survey is to determine the number and placement of access points needed to provide adequate coverage and capacity for the desired applications.

In this case, the engineer is designing for high-speed data and voice in an indoor office. This implies that the network should be able to support both data traffic and voice traffic, which requires certain quality of service (QoS) parameters to be met, such as low latency and jitter.

To determine the recommended data rate for optimal VoWLAN design, we need to consider the minimum data rate required for good voice quality and the signal strength needed to achieve that data rate. The signal strength is typically measured in dBm, which is a logarithmic scale that represents the power ratio in decibels relative to one milliwatt (dBm = 10 log10(P/1mW)).

The recommended data rate for VoWLAN design is typically based on the following criteria:

1. Latency: VoIP requires low latency, typically less than 150ms, to maintain good voice quality.
2. Jitter: VoIP also requires low jitter, which is the variation in latency over time. Jitter can cause voice packets to arrive out of order, leading to poor voice quality.
3. Bandwidth: VoIP requires a relatively low bandwidth, typically around 100 kbps per call, but this can vary depending on the codec used.

Based on these criteria, the recommended data rate for VoWLAN design is typically 12 Mbps or higher, as this provides enough bandwidth to support VoIP and other data traffic while maintaining low latency and jitter.

In this question, the signal strength is given as -67 dBm. To achieve a data rate of 12 Mbps or higher at this signal strength, we need to use a wireless standard that supports high data rates and has good signal strength at this level.

Option A (6 Mbps on 802.11 bgn) and option B (24 Mbps on 802.11 bgn) both use the 802.11 b/g/n wireless standard, which supports data rates up to 54 Mbps but may not provide good signal strength at -67 dBm.

Option C (12 Mbps on 802.11 an) and option D (24 Mbps on 802.11 an) both use the 802.11 a/n wireless standard, which supports data rates up to 300 Mbps and provides better signal strength at -67 dBm.

Therefore, the recommended data rate for optimal VoWLAN design with a -67 dBm signal level is either option C (12 Mbps on 802.11 an) or option D (24 Mbps on 802.11 an).