Exam 300-425 topic 1 question 3 discussion

Answer is C. - CCNP official guide, Chapter 5, Section Designing a Wireless Network for Voice and Video: A better approach is to limit transmissions to use higher data rates so that stations transmit a frame and get off the air sooner, allowing other stations an opportunity to use the channel. That ultimately affects latency and jitter—parameters that are critical for acceptable voice and video performance. You should configure 12Mbps as the lowest and only mandatory data rate, while disabling all rates below that. All data rates greater than 12Mbps should be configured as supported so that they can be used by any device and application as RF conditions permit. - 802.11b supports max 11 Mbps.

C - ‘For voice or real-time application support, 12Mbps is common, and 24Mbps is expected if real-time video applications (for example, video conferencing) are your target. Here again, as most cells carry both data and voice, designing around 12Mbps minimum has become common even for data-only support, in anticipation of occasional voice activity.’ Official Cert Guide, Ch.3. p.60. para.3.‘As you plan the band and channel assignment for each AP, try to leverage the 5GHz band as much as possible.’ Official Cert Guide, Ch.5. p.106. para.4.‘You should configure 12Mbps as the lowest and only mandatory data rate, while disabling all rates below that.’ Official Cert Guide, Ch.5. p.107. para.2.

Need to correct my previous answer, I say D is correct , 12Mbps is the minimum rate but to having better voice and more call we need higher data rate, while using low data rate we use more airtime of each channel . 24 Mbps minimizes airtime usage, supports more simultaneous calls, and ensures lower latency and jitter.

C is correct .

I would sayt "it depends" of the number of simultaneous call to place

answer is A, please check the data rate. We traditionally use 2.4ghz to do the predicative, and 802.11b only have11 mbps, therefore, A is answer.

Source - https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/Voice.pdf "For a high density deployment or a deployment where a large number of calls are required in a small floor space, 11a is recommended because of the number of channels and the 54 Mbps data rate. The lower data rates in 11a can be disabled, the 24 Mbps data rate can be set to “required”, and the rates of 36 to 54 can be left enabled. "

Official CCNP book page 60: For basic data coverage, 6Mbps is common. For voice or real-time application support, 12Mbps is common, and 24Mbps is expected if real-time video applications (for example, video conferencing) are your target. Here again, as most cells carry both data and voice, designing around 12Mbps minimum has become common even for data-only support, in anticipation of occasional voice activity. So the answer is C

VoWLAN. min -67dbm and 12 Mbps

I think the answer is D. I found this in the VoWLAN Design recommendations: Coverage cells can be created for specific data rates. For a high density deployment or a deployment where a large number of calls are required within a small floor space, 802.11a is recommended because of the number of channels and the 54 Mbps data rate. The lower data rates in 802.11a can be disabled, the 24 Mbps data rate can be set to required, while the 36 to 54 Mbps data rates can be left enabled.

If it weren't for the question throwing "high-speed" and "optimal" in there, I would say 12Mbps, which is definitely the minimum specification. However, I believe they are looking for 24Mbps.

when designing for voice, you have to think about RTP streams. from cisco study guide: (an now you can choose C or D) " voice calls use bidirectional RTP streams to transport audio. Each call uses two separate streams, but they cannot be transmitted simultaneously because of channel contention. At a 24Mbps data rate, up to 27 simultaneous bidirectional RTP streams can exist, or up to 13 calls."

It's definitely answer C In voice and video design you should configure 12 Mbps as the lowest and only mandatory data rate.

Provided answer is correct, the question involves a predictive site survey requirements, there are current and legacy VoWLAN environments that can utilize b with the overlapping channels for voice, however not recommended, but is important for predictive survey purposes. Here is the Cisco white page link ref. chapter 11-12. https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/Voice.pd

the right answer is c because at 24mbs 802.11b cannot scale and your adviced to stick to the 5ghz band which gives us 12mbs for voice and 24mbs for video

i will go for C - because there are asking - What is the recommended data rate withגˆ’-67 dBm signal level for optimal VoWLAN design? - -67dBm should be edge so there should be the lowest enabled data rate 12Mbps

"The lower data rates in 11a can be disabled, the 24 Mbps data rate can be set to “required”, and the rates of 36 to 54 can be left enabled. " https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/Voice.pdf