Feedback through Overhearing

In this paper we examine the value of feedback that comes from overhearing, without dedicated feedback resources. We focus on a simple model for this purpose: a deterministic two-hop interference channel, where feedback comes from overhearing the forward-links. A new aspect brought by this setup is the dual-role of the relay signal. While the relay signal needs to convey the source message to its corresponding destination, it can also provide a feedback signal which can potentially increase the capacity of the first hop. We derive inner and outer bounds on the sum capacity which match for a large range of the parameter values. Our results identify the parameter ranges where overhearing can provide non-negative capacity gain and can even achieve the performance with dedicated-feedback resources. The results also provide insights into which transmissions are most useful to overhear

Capacity of 1-to-K Broadcast Packet Erasure Channels with Channel Output Feedback

This paper focuses on the 1-to-K broadcast packet erasure channel (PEC), which is a generalization of the broadcast binary erasure channel from the binary symbol to that of arbitrary finite fields GF(q) with sufficiently large q. We consider the setting in which the source node has instant feedback of the channel outputs of the K receivers after each transmission. Such a setting directly models network coded packet transmission in the downlink direction with integrated feedback mechanisms (such as Automatic Repeat reQuest (ARQ)). The main results of this paper are: (i) The capacity region for general 1-to-3 broadcast PECs, and (ii) The capacity region for two classes of 1-to-K broadcast PECs: the symmetric PECs, and the spatially independent PECs with one-sided fairness constraints. This paper also develops (iii) A pair of outer and inner bounds of the capacity region for arbitrary 1-to-K broadcast PECs, which can be evaluated by any linear programming solver. For most practical scenarios, the outer and inner bounds meet and thus jointly characterize the capacity.Comment: 8 pages, 2 figures. Published in Allerton 2010. The journal version of this work was submitted to IEEE Trans IT in May, 201

Fly on the wall: can students' learning be enhanced by allowing them to witness their own summative assessment and feedback event?

The Design studio learning system within New Zealand Tertiary Design Schools has a unique critique method, (often called 'The Crit'); The Crit event itself is rather a 'veiled' process and has been analyzed and written about extensively. There has also been some negative feedback from students that this form of critiquing process is not necessarily a good type of feedback process. Is there a method that protects the student's privacy related to his or her own design work and at the same time maintains the Design School's integrity of supplying reasoned and fair assessment within the wider Profession? A field trial scenario was designed and arranged with a group of volunteer design students, so each in turn, could sit-in and witness their own assessment / feedback session. This paper reports on this field trial, (timed to occur after the critique). This paper analyses this experiment, exploring the field trial responses, looking for links within a wider Educational literature base to the ground this 'Fly on the Wall' scenario within known pedagogies. NB. This scenario is not proposing to supplant 'The Crit,' rather the intention being in addition to it

DMT Optimal Cooperative Protocols with Destination-Based Selection of the Best Relay

We design a cooperative protocol in the context of wireless mesh networks in order to increase the reliability of wireless links. Destination terminals ask for cooperation when they fail in decoding data frames transmitted by source terminals. In that case, each destination terminal D calls a specific relay terminal B with a signaling frame to help its transmission with source terminal S. To select appropriate relays, destination terminals maintain tables of relay terminals, one for each possible source address. These tables are constituted by passively overhearing ongoing transmissions. Hence, when cooperation is needed between S and D, and when a relay B is found by terminal D in the relay table associated with terminal S, the destination terminal sends a negative acknowledgment frame that contains the address of B. When the best relay B has successfully decoded the source message, it sends a copy of the data frame to D using a selective decode-andforward transmission scheme. The on-demand approach allows maximization of the spatial multiplexing gain and the cooperation of the best relay allows maximization of the spatial diversity order. Hence, the proposed protocol achieves optimal diversitymultiplexing trade-off performance. Moreover, this performance is achieved through a collision-free selection process

Implementation and evaluation of the sensornet protocol for Contiki

Sensornet Protocol (SP) is a link abstraction layer between the network layer and the link layer for sensor networks. SP was proposed as the core of a future-oriented sensor node architecture that allows flexible and optimized combination between multiple coexisting protocols. This thesis implements the SP sensornet protocol on the Contiki operating system in order to: evaluate the effectiveness of the original SP services; explore further requirements and implementation trade-offs uncovered by the original proposal. We analyze the original SP design and the TinyOS implementation of SP to design the Contiki port. We implement the data sending and receiving part of SP using Contiki processes, and the neighbor management part as a group of global routines. The evaluation consists of a single-hop traffic throughput test and a multihop convergecast test. Both tests are conducted using both simulation and experimentation. We conclude from the evaluation results that SP's link-level abstraction effectively improves modularity in protocol construction without sacrificing performance, and our SP implementation on Contiki lays a good foundation for future protocol innovations in wireless sensor networks

Office design for the multi-generational knowledge workforce

Purpose – The purpose of this paper is to evaluate the impact the workplace can have on knowledge working for a multi-generational workforce. Design/methodology/approach – A case study analysis is undertaken of Leeds City Council (LCC) workplace in the UK. Findings – The findings from the study show that in the context of LCC there are some key differences between the generations regarding knowledge working preferences for formal/informal meeting spaces. In other aspects, such as knowledge sharing, the generations appear to agree on key aspects such as mentoring and team-based working environments. Practical implications – Corporate real estate managers can use the research findings to assist them in providing a range of workplace settings to enhance multi-generational interaction. Originality/value – This paper fills a gap in current research by evaluating workplace preferences based on generational differences.</p