Bursty nature of telephony

hello

From wiki..
''There are a fixed number of orthogonal codes, timeslots or frequency bands that can be allocated for CDM (Sync CDMA), TDMA, and FDMA systems, which remain underutilized (to fail to utilize fully) due to the bursty nature of telephony and packetized data transmissions. ''

My question is what does the bursty nature of telephony mean actually? So far I understnad - bursty nature means sometime very high number of transmission (i.e. phone calls) while other time it might be very low number of transmission? And when the number of calls are very low, the codes/time slots/ frequency bands are unused, hence underutilized.

Is it right what I understand?

Thanks

It can mean a couple of things. One is syllabic nature of voice, other is 'you talk then I talk'.

For cellular there is utillization improvements on both these accounts. First is vocoder based compression, second is placing other data (text, multimedia) during gaps in speech.

Most modern phones accept variable rate compression. When system use is heavy the cellular system can increase the compression reducing bit rate allowing more capacity, at reduced voice quality.