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UID:www.tcs.tifr.res.in/event/599
DTSTAMP:20230914T125931Z
SUMMARY:Broadcast Channels and Their Capacity Under Noisy Feedback
DESCRIPTION:Speaker: Vinod M. Prabhakaran\n\nAbstract: \nAbstract: Broadcas
 t channels model the downlink in a wireless network\, i.e.\, the link from
  a base station transmitter to several receivers. The broadcast channel mo
 del was proposed by Tom Cover in 1972. While characterizing the capacity r
 egion of the broadcast channel remains an important open problem in Inform
 ation Theory\, the capacity of the Gaussian version of this channel has be
 en resolved (single antenna version in 1974 and multi-antenna version in 2
 005).\n\nFeeding signals received from the channel by the receiver(s) back
  to the transmitter(s) may\, in general\, lead to an enlargement of the ca
 pacity region of multi-terminal channels. A famous exception to this rule 
 is the point-to-point channel (i.e.\, a single transmitter & a single rece
 iver). For a limited class of broadcast channels\, called the physically d
 egraded broadcast channels\, feedback does not enlarge the capacity region
  (El Gamal\, '78\,'81). However\, this class does not contain wireless cha
 nnels which arise in practice.\n\nResults available in the literature show
  that feedback of even a limited form can result in an enlargement of the 
 capacity region of broadcast channels. Full feedback (Dueck '80\, Ozarow-L
 eung '84)\, feedback from only one receiver (Pillai '08)\, noisy feedback 
 (Shayevitz-Wigger '13\, Venkataramanan-Pradhan '13)\, rate-limited feedbac
 k (Yu-Wigger '14) have all been shown to lead to an enlargement of the cap
 acity region in channels of practical interest. For multiple access channe
 ls (the uplink analogue of broadcast channels)\, it is known that even par
 tial noisy feedback always enlarges the capacity region. A duality which i
 s known to exist between multiple access and broadcast channels has led to
  the speculation that a similar result may hold for broadcast channels. We
  show that this is not the case in a class of channels which includes chan
 nels which arise in practice. In particular\, we identify a threshold for 
 the noise power in the feedback link above which feedback from a single re
 ceiver does not enlarge the capacity region (joint work with Sibiraj B Pil
 lai (IIT Bombay).\n
URL:https://www.tcs.tifr.res.in/web/events/599
DTSTART;TZID=Asia/Kolkata:20150514T160000
DTEND;TZID=Asia/Kolkata:20150514T170000
LOCATION:A-212 (STCS Seminar Room)
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