Online Estimation of RF Interference

Nabeel Ahmed, Usman Ismail, Srinivasan Keshav and Konstantina Papagiannaki

In enterprise networks in which the thin access points are managed by a single controller, there is much room for optimization. As a example, interference between access points can be prevented if a conflict graph is available.

The authors implement a novel mechanism to build such conflict graph. Instead of using lengthy bandwidth probes, they introduce the concept of microprobes. The idea is to attempt transmission from two access points simultaneously. If one of the access points hold the transmission until the other has finished, it means that the two access points are in carrier-sense range, which is quite common in enterprise networks.

The lack of ack may indicate that the APs are hidden from one another, and the simultaneous transmission prevented the receiver to correctly decode the packet.

The implementation of the idea poses a variety of challenges. The APs have to be sychronized, and the delay ellapsing from the controller order to the actual probe has to be minimized. Further, the network has to be silenced before the probe. Then it is necessary to accurately measure the MAC service time. The authors solved all the problems and attained an accuracy comparable to the one obtained from traditional bandwidth probes.

The advantage of the microprobes is that they can be performed in a few ms, which allows to build the conflict graph during the network normal operation (no downtime required).

I am particularly interested in the possibility to tinker with the wlan card microcode, since it would allow me to build a testbed of my idea.

panacea

The idea is pretty simple:do not decrement the backoff counter of stations in deterministic mode in busy slots.

A Capacity Analysis for the IEEE 802.11 MAC Protocol

Y.C. Tay and K.C. Chua

The article presents a model of IEEE 802.11 that is completely different from Bianchi's approach and thus provides different insights in the protocol. I would say it is a must read and a strong candidate for our wireless seminars.

System Centric and User Centric Queueing Models for IEEE 802.11 based Wireless LANs

Kamesh Medepalli and Fouad A. Tobagi

The authors make use of queueing theory to analyse DCF. Hopefully this article helps me to understand Boris model. The ultimate goal is to model CSMA/ECA

A Singular Choice for Multiple Choice

Gudmund S. Frandsen Michael I. Schwartzbach

Multiple-choice-test theory. It is not clear to me whether it is applicable to multiple-choice multiple-answer tests.

A wireless sensor networks MAC protocol for real-time applications

E. Egea-Lopez Æ J. Vales-Alonso Æ A. S. Martınez-Sala Æ J. Garcıa-Haro Æ
́ ́ ́
P. Pavon-Marino Æ M. V. Bueno Delgado
́ ̃
This protocol has some similarities with our proposal CSMA/ECA.

Education Should Consider Alternative Formats for the Dissertation

Nell K. Duke; Sarah W. Beck

The authors explain that traditional dissertations suffer from two shortcomings. First, they have an extremely limited readership. Often, the members of the jury are the only readers of the dissertation. Then, the heavy tome gathers dust in the library archive.

Second, writting the dissertation is a one-time tremendous effort that does not train the researcher for her future proffessional writting activities, which include soliciting funds in project proposals and disseminating the results in the form of articles in scholary forums.

The authors advocate for a dissertation in the form of articles ready to be sent for publications. The articles should stem from a single research project, but they may include different methodologies and present different conclusions.

I completely agree with the rationale of the paper.

A tutorial survey on vehicular ad hoc networks

H. Hartenstein, K. P. Laborteaux

This review will be very helpful in preparing our paper for VTC.

... roadside units.
... 802.11p -> Csma also in vehicular networks
... periodical and event-driven traffic
... congestion in the roadnetwork might translate into congestion in the radio access network

A new technique for satellite broadcast channel communication

F.Borgonovo and L.Fratta

The authors propose an hybrid aloha/reservation protocol. It behaves as aloha until a collision occurs. Then switches to reservation.

I am specially interested in this sentence:
Moreover we can say that the S-ALOHA technique is very suitable for low traffic, single-packet, condiditions even if a control scheme has to be used to guarantee the system stability.

and cites this paper:
Lam, S. and Kleinrock, L. "Packet Switching in a Multiaccess Broadcast Channel: Dynamic Control Procedures"

FreeMAC: Framework for Multi-Channel MAC Development on 802.11 Hardware

Ashish Sharma, Elizabeth M. Belding

The authors present a solution for multi-channel wifi. What really impressed me is the high degree of control over the network interface that is achieved. If I had the chance to reproduce their work, it would be applicable to suppress acks or to test our csma/eca proposals.

Using chunk collision avoidance to optimize p2p live

When a group of nodes under the same authoritative domain (or ISP) collectively download a P2P video stream, it is desirable to minimize inter-ISP traffic. Ideally, each chunk of the stream would be downloaded by one of the nodes from an external peer, and then shared among all the nodes under the same ISP. If the same chunk is downloaded from external sources by to different peers of the same ISP, we can say that a "collision" happened. Enhanced collision avoidance techniques from MAC layer can be used in order to optimize the P2P live streaming download.

Will IPTV ride the peer-to-peer stream?

Marfia, G., Sentivelli, A., Tewari, S., Gerla, M. and Kleinrock, L.

The article concludes that ADSL's asimmetry is the main obstacle in the way of high-quality P2P IP TV.

Multiuser Detection in Large Systems with an unknown Number of Users

Adrià Tauste Campo, Albert Guillén i Fàbregas and Ezio Biglieri

It addresses the same problem as the previous article. To my particular taste, this was much more understandable than the previous one, even though it is still ongoing work.

Large-system analysis of a CDMA dynamic channel under a Markovian input process

Ezio Biglieri∗ , Emanuele Grossi† , Marco Lops† , and Adrià Tauste Campo


It addresses the problem of a communication system with an unknown number of users. It is curious that to see that the estimation of the number of users is completely different from what I have been reading so far. Even if the problem statement might sound similar, it is actually a completely different problem.

High-Performance Wireless Ethernet

Heegard, Coffey, Gummadi, Murphy, Provencio, Rossin, Schrum, Shoemake

A review of IEEE 802.11 in its early stages with emphasis on coding.

learning MAC protocol for sensor networks

Assume a network of sensor that periodically transmit some data. The period T is the same for all the sensors. Assume also that the time required to tranmsit a packet is much shorter than the period Tx << T. Then we propose a MAC protocol that, in case of collision, re-attempt transmission after a random period of time R, Tx<< R << T. After a successful transmission, the sensor delays exactly T the new transmission attempt.

After the learning period, the system will operate collision-free. Further, each node will transmit deterministically each T seconds. The receiver can sleep for most of the time, and only wake up when it knows that there will be an incoming packet.

Weighted Fair Uplink/Downlink Access Provisioning in IEEE 802.11e WLANs

Feyza Keceli, Inanc Inan, and Ender Ayanoglu

A comprehensive solution to the uplink/downlink unfairness in EDCA. The goodies include:
i) Fully .11e compliant.
ii) Smooth interaction with TCP.
iii) Maintains the priorities of the queues.
iiii) Satisfactory QoS for real-time flows.

EBA: An Enhancement of the IEEE 802.11 DCF via Distributed Reservation

Jaehyuk Choi, Joon Yoo, Sunghyun Choi, Member, IEEE, and Chongkwon Kim, Member, IEEE

Very interesting paper. I need to organize my thoughts. The core idea is brilliant: the stations advertise their backoff values. I have the feeling that the proposed implementation can be improved.

Merits: It proactively prevent collisions from the very beginning. In comparition, CSMA/ECA has a transitory operation with performance similar to legacy CSMA/CA. In can tolerate a large number of stations delivering acceptable throughput and fairness.

Shortcomings: It requires the modification of the MAC headers, which makes the coexistence with legacy stations trickier. The collision avoidance mechanism relies in additional signaling included in those header. If errors or collisions occur, that signaling is lost and the operation of EBA falls to the same as legacy CSMA/CA.

A Reservation-Based Enhancement of IEEE 802.11 DCF Protocol

Mehdad N. SHIRAZI†a) , Nonmember, Oyunchimeg SHAGDAR†† , Suhua TANG†† , Masanori NOZAKI††† ,
Youiti KADO††† , and Bing ZHANG† , Members

An Explanation for Unexpected 802.11 Outdoor Link-level Measurement Results

Giustiniano, D. Bianchi, G. Scalia, L. Tinnirello, I.
This is a hands-on paper. Very well written and interesting. It shows that the combination of atheros chipset and madwifi drivers present a weird effect because of the particular use of the diversity concept.

Performance Evaluation of R-ALOHA in Distributed Packet Radion Networks with Hard Real-Time Communications

Te-Kail Liu, John A. Silvester and Andreas Polydoros

They analyze R-Aloha, which is very similar to CSMA/ECA. And they also use markov chains, so the parallelisms arise. Nevertheless, since there is no reservation in CSMA/ECA, there are also some differences. Anyway, there is still many things I can learn and reuse in this paper. By the way, which is the difference between p[] and Pr{}?

Aloha Packet System with and without Slots and Capture

Lawrence G. Roberts

This paper is written using a typing machine. The author considers the capture effect for satellite communication.

Capture Effects of Wireless CSMA/CA Protocols in Rayleigh and Shadow Fading Channels

Jae Hyun Kim, Member, IEEE, and Jong Kyu Lee, Member, IEEE

The performance of CSMA/CA is computed, taking into account the capture effect. I was surprised that they also considered the case in which acks are ommitted.

IMS-controlled ethernet domains for networked services delinvery

D.Tolle, A.Plankl, G.Butscher

Using ethernet as a transport plane for IMS

Application Layer FEC in IPTV Services

M.Luby. T.Stockhammer, M.Watson

Forward Error Correction has many applications in IPTV distribution. I was thinking that it maybe also particularly useful for P2P live streaming.

Game Theory for Wireless Engineers

Allen MacKenzie, Luiz DaSilva

A superb book to get a flavor about what game theory is about.

Congestion-Aware Rate Adaption in Wireless Networks: A Measurement-Driven Approach

P. Acharya, A. Sharma, E. Belding, K. Almeroth and K. Papagiannaki

Channel Busy Time is used to detect congestion.A functionality of the MadWifi driver is used to obtain CBT in real time. It is also detailed how the ill-implemented auto-rate fallback aggravates the congestion situation. A new rate adaptation mechanism is proposed and the overall performance is notoriously improved in congested networks.

Can I add a VoIP call?

Garg and Kappes

So many interesting things in five pages.

The main limitation comes from packet loss, reported to be 16%.

Quoting:While in wired networks (such as Ethernet) choice of codecs is highly effective in dealing wiith network load, in 802.11 networks, this is not the case.

Performance Analysis of the IEEE 802.16 Wireless Metropolitan Area Network

Worth reading to learn a bit about .16. The results and plots are naive.

A WAITING-TIME DEPENDENT BACKOFF ALGORITHM FOR QOS ENHANCEMENT OF VOICE OVER WLAN

Jing Chi Yajuan Wang Bo Xia Ruozhou Lin Xian Gao

The authors propose to adjust the backoff window as a function of the time that the packet has been waiting to be sent. After a certain threshold, the backoff window is reduced for each new attempt. When the packet has been excessive delayet, it is simply discarded.

Detecting MAC Layer Collision Abnormalities in CSMA/CA Wireless Networks

Alberto López Toledo, Xiaodong Wang

Really interesting. I have some minor doubts that I would ask to Alberto when I have the chance.

IEEE 802.11s: WLAN Mesh Standardization and High Performance Extensions

Guido R. Hiertz, Yunpeng Zang, Sebastian Max, Thomas Junge, Erik Weiss, Benedikt Wolz,
RWTH Aachen University
Dee Denteneer, Philips Research
Lars Berlemann and Stefan Mangold, Swisscom


The headache of wireless mesh networks. It seems that there is no magic formula to solve the problem. To limit interference while maximizing space reuse. The article suggests the use of beacons to separate traffic of the stations and mesh nodes. This beacons would also include SNR measurements, reservation information...

Maybe the solution lies in the use of smart antennae. I would comment it this afternoon with Pere.

SIP-BASED MOBILITY MANAGEMENT IN NEXT GENERATION NETWORKS

STEFANO SALSANO AND ANDREA POLIDORO, UNIVERSITY OF ROME TOR VERGATA
CHIARA MINGARDI AND SAVERIO NICCOLINI, NEC EUROPE LTD.
LUCA VELTRI, UNIVERSITY OF PARMA

I see a parallelism betwen this paper and the previous one. In both cases a problem (mobility/multicast) has been atttempted to solve at the network layer for a long time and, now, efforts are focused at the application layer.

Opportunities and Challenges of Peer-to-Peer Internet Video Broadcast

By Jiangchuan Liu, Member IEEE , Sanjay G. Rao, Bo Li, Senior Member IEEE , and Hui Zhang

This is the paper for the next journal club.

Network Coding for Efficient Multicast Routing in Wireless Ad-hoc Networks

Jingyao Zhang, Pingyi Fan, Member, IEEE, and Khaled Ben Letaief, Fellow, IEEE

Network coding might be efficient for multicast in adhoc and sensor networks. This papers deal with the problem of finding which nodes have to be encoders.

Topological Design of Interconnected LANs Using Hopfield Neural Networks

Shih-Tsung Yang and Anthony Ephremides

Hopfield Networks are applied to LAN interconnection for minimal delay.

Performance anomaly of 802.11b

Martin Heusse, Franck Rousseau, Gilles Berger-Sabbatel, Andrzej Duda

When a slow station shares the channel with fast stations, all the stations experiment low throughput. This problem is alleviated when using TCP, since the lost packets prevent that the TCP windows fully open.

This reference is also important. It is the one to cite when referring to short-term unfairness in DCF.

An analysis of short-term fairness in wireless media
access protocols,

IEEE 802.16 Mesh Schedulers: Issues and Design Challenges

Najah A. Abu Ali,Abd-Elhamid M. Taha and Hossam S. Hassanein Hussein T. Mouftah

My intention was to get a feeling about mesh in 802.16... As I was reading, I was overwhelmed by the immense number of issues that one has to take into account... I wonder whether such a complex operation mechanisms would even work in a real implementation.

Adaptative Optimization of IEEE 802.11 DCF Based on Bayesian Estimation of the Number of Competing Terminals

A. López Toledo, T. Vercauterenm and X. Wang
Sequential Monte Carlo methods combined with a Bayesian approach is use to estimate the number of competing terminals to optimizw DCF parameters.

Voice Capacity Analysis of WLAN with Channel Access Prioritizing Mechanism

X. Ling,Y.Xeng,W. Shen, J. Mark

Most of the research in WLAN performance departs from the assumption of saturated stations. This was my motivation to write the WONS paper. In this article, the issue is solved in an elegant way. As a plus, they are capable to take into account different classes for QoS.

The article itself is divided in two parts. The first one studies the competition for the channel between VoIP and saturated sources in adhoc networks. The second part deals with the AP bottleneck problem when infrastructure operation. IMHO there is no tight relationship between the two parts of the articles, because the focus is placed in different problems.

Nevertheless, the article is well written, and will be an inspirations (and references) sources when writing my own articles.

C-PRMA: A Centralized Packet Reservation Multiple Access for Local Wireless Communications

G. Bianchi, F. Borgonovo, L.Fratta, L. Musumeci, M.Zorzi

Centralized PRMA is an extension of PRMA that includes a centralized scheduler that handles traffic hetereogeneity. IMHO the complexity is overwhelming.

The paper will be useful because its thorough introduction.

T ree Algorithms for Packet Broadcast Channels

JOHN I. CAPETANAKIS

This paper introduces the concept of tree algorithms. The address space is divided in two halves. In two successive slots, the one is devoted to the first halve and the second to the second halve. If there is a collision, the address spaces is subsequently divided in two. Again the stations belonging to the first part transmit in the first slot while the stations included in the second part transmit in the second slot. This algorithm is repeated until all the stations have transmittet their packets.

Even though the proposal is theoretically sound and leads to throughput of 0.3-0.4 packets per slot, it probably present practical disadvantages. It was proposed in 1979 and we have not seen any implementation yet.

Design and Analysis of Cross-Layer Tree Algorithms for Wireless Random Access

Xin Wang, Member, IEEE, Yingqun Yu, Student Member, IEEE, and Georgios B. Giannakis, Fellow, IEEE

The reading of this paper resulted in many additional taks to do:
- There is a formula that is clearly wrong. Must find out what's goin' on
- It talks about tree algorithms for contention. What are this TA exactly?
- In the jitel paper, I didn't explain how to calculate the efficiency for the BEB case.
- The authors neglect the slots different lengths. Why? Is it because in 802.16 all the slots have equal length?
- Should I include this paper in the related work?

Mobile Privacy in Wireless Networks–Revisited

Caimu Tang, Member, IEEE, and Dapeng Oliver Wu, Senior Member, IEEE

The authors detail the privacy requirements for mobile dives and propose a mechanism to attain such privacy. It is based on Elliptic Curve Cryptography and thus does not place overwhelming burden on the mobile device.

Analysis of the Stability and Performance of Exponential Backoff

Byung-Jae Kwak,Nah-Oak Song,Leonard E. Miller

An extensive analysis of Exponential Backoff and its asymptotic properties is provided. Unfortunately, the truncated exponential backoff which is the one that actually appears in real implementations is not considered.

A Capacity Analysis for the IEEE 802.11 MAC Protocol

Y.C. TAY and K.C. CHUA

Very interesting paper. The author provide a number of claims related to DCF that enhance the understanding of the protocol. They already highlight that the optimal transmission probability is a function of the packet length and the number of active terminals.

IEEE 802.11 Wireless Local Area Networks

Brian P. Crow, Indra Widjaja, Jeon Geun Kim, Prescott T. Sakai

Even thoug I could not finish the paper (the scanning is horrible) I had to write a comment. These guys already obtained results than me... and it was back in the 20th century :-P

VARIABLE BIT RATE VOIP IN IEEE 802.11E WIRELESS LANS

FRANK HAIZHON LI, UNIVERSITY OF SOUTH CAROLINA UPSTATE
YANG XIAO AND JINGYUAN ZHANG, UNIVERSITY OF ALABAMA

The article presents CAC for VBR VoIP calls. The variable bit-rate is a consequence of the on-off nature of the calls. The authors present a time-based admission control mechanism that uses token-bucket and relies on the observation information to decide whether to accept a new call or not. Additionally they propose that the AP accesses the channel with priority to solve the uplink-downlink unfairness.

EVALUATION OF SIGNALING LOADS IN 3GPP NETWORKS

DARIO S. TONESI AND LUCA SALGARELLI, UNIVERSITY OF BRESCIA
YAN SUN AND THOMAS F. LA PORTA, PENNSYLVANIA STATE UNIVERSITY

The article compares the signaling load of 3GPP release 99 to release 5. The long SIP text messages and the higher number of messages are responsible of increased signaling traffic.

sempre 16

Quan una estació ha d'elegir un backoff després de transmetre un paquet amb èxit, calcula un valor aleatori entre 0 i CWmin. Per què no elegir sempre 16? D'aquesta manera després d'un transitori amb col.lisions, el sistema es comportaria com un TDMA.

z-mac: a hybrid mac for wireless sensor networks

Injong Rhee, Ajit Warrier, Mahesh Aia and Jeongki Min

I got the idea of what a hybrid protocol is. A combination of csma and tdma. It seemed to me that the proposal is excruciatingly complex and tedious. However, i must check the following references:

[13] K. Jamieson, H. Balakrishnan and Y. Tay. Sift:A MAC protocol for event driven wireless sensor networks

[19] Y. Tay, K. Jamieson, and H. Balakrishnan. Collision-Minimizing CSMA and its applications to wireless sensor networks

Optimal Constant-Window Backoff Scheme for IEEE 802.11 DCF in finite Load Single-Hop Wireless Networks

Hicham Anouar and Christian Bonnet

The authors propose using an optimal fixed window which is computed as a function of the number stations. There is a weird assumption related to a "normalized packet length". I found a few details that could be useful in refining my own paper.

I was surprised to see that they have a journal version of the same paper.

SOSIMPLE: A Serverless, Standards-based, P2P SIP Communication System

David A. Bryan and Bruce B. Lowekamp, Cullen Jennings

I read this as an introduction to P2PSIP, before attempting to understand the RFCs.

Batch and Sequential Bayesian Estimators of the Number of Active Terminals in an IEEE 802.11 Network

Tom Vercauteren, Alberto Lopez Toledo

Following Toledo's trail, I read this paper in which the authors describe how to estimate the number of active stations in a IEEE 802.11 network. Bayesian algorithms are used to construct a number of off-line and on-line estimators with different degrees of complexity and accuraci.

Event thought I could not grasp the mathematical core, the references will be quite useful, since I am also working on optimizing the network performance for a variable number of stations. Further, the description of the simulations can be used as a reference for future works.

A Robust Kolmogorov-Smirnov Detector for Misbehavior in IEEE 802.11 DCF

Alberto Lopez Toledo and Xiaodong Wang

The proposal is to measure the number of empty slots between transmissions of a given station. Then use the K-S technique to estimate the cdf and compare to the expected cdf. When the actual cdf clearly differs from the expected cdf, it is inferred that the node is missbehaving.

Stability and Performance of the R-ALOHA Packet Broadcast System

SHUJI TASAKA

R-Aloha differs from Aloha in the fact that a stations implicitly obtains a reservation for the channel whenever it successfully transmits a packet. The slots are grouped in frames, and the station obtains a reservation in each frame. This idea is interesting because in steady state operation, collisions are avoided and the system operates as in tdma.

The mathematical tool used in the analysis is Equilibrium Point Analysis (EPA)

Enhancement of IEEE 802.11 Distributed Coordination Function with Exponential Increase Exponential Decrease Backoff Algorithm

Nah-Oak Song, Byung-Jae Kwak, Jabin Song, Leonard E. Miller

Short paper that proposes an alternative to the doubling of the contention window and evaluates the new proposal using simulation

Stability of Binary Exponential Backoff

JONATHAN GOODMAN et al

Hard-core mathematical stuff. It comes at no surprise since the paper is written in a mathematical institute. Maybe the references are of some use.

Using Incompletely Cooperative Game Theory in Wireless Mesh Networks

Liqiang Zhao and Jie Zhang, University of Bedfordshire
Hailin Zhang, Xidian University

The inclusion of game theory in the title might sound scary, but the paper is not complicated. It inspired me the idea of looking for more efficient backoff mechanisms.

new backoff scheme

The current backoff scheme is independent of the number of contending stations. The result is that is desirable to adjust CWmin to its optimum value. I've been thinking about a backoff algorithm that reacts and adapts to the number of active contending stations.

Solutions to Performance Problems in VoIP Over a 802.11 Wireless LAN

Wei Wang, Soung Chang Liew, and Victor O. K. Li
This paper already highlight the main impairments in VoWLAN: Protocol overhead and uplink/downlink unfairness.
Their solution (M-M) consists on multiplexing-multicasting the packets for download. These multicasted packets require strict prioritization to avoid collision.

The main drawback I can see is how could be this combined with level-2 security (WPA) so widespread this days.

The authors also analyze the impact their solution has on delay and the impact of elastic flows on the number of VoIP Streams.

A New Access Control Solution for a Multi-Provider Wireless Environment

ARTUR HECKER et al.

Maybe it is because monday morning, but could not get the point. It was something about 4G and a smart card similar to a sim.

Verification of Common 802.11 MAC Model Assumptions

David Malone and Ian Dangerfield and Doug Leith

Very interesting paper that compare values obtained from the models with those obtained from testbeds. Again, it is something that I was thinking to be necessary. Additionally there are many references I must read.

Inter-Vehicle Communications

Marc Torrent Moreno

This thesis studies IVC based on 802.11p, a variant of 802.11 for vanet. After describing the general characteristics of this kind of networks and introducing a modification of ns-2 specifically for vanets, proposes two new protocols. One for power control that avoids channel congestion, the other for fast propagation of emergency information. The two protocols are evaluated using the simulator.

Design of QoS and Admission Control for VoIP Services over IEEE 802.11e WLANs

Pei-Yeh Wu1, Yu-Chee Tseng1, and Hewitt Lee2

I liked it. It's about something I had been thinking and I think that I can learn something from their work.

ANALYSIS OF RETRY LIMIT FOR SUPPORTING VOIP IN IEEE 802.11E EDCA WLANS

Byung Joon Oh

Not a outstanding paper. But we have to admit that we were not the first that came up with the idea of suppressing/reducing retransmissions.

A new MAC protocol ensuring the multimedia traffic QoS for CDMA networks

Loren Carrasco, Guillem Femenias, Felix Raja

I was curious about this paper from people from my Island. It remebered me to take a look at the on-off model.
I should find some additional information in this paper:
G. Bianchi and F. Borgonovo et al., “C-PRMA: A Centralized Packet Reservation Multiple Acces System for
Local Wireless Communications”, IEEE Transactions on Vehicular Technology, Vol. 46, No. 2, pp. 442–435,
1997.

Uplink RRM for conversational and interactive services in utra-fdd

O.Sallent, J.Perez-Romero, R.Agustí

I read it because it was referenced in the paper i was reviewing.

Do we need Header Compression for VoIP in Wireless LANs?

Rastin Pries, Andreas Maeder and Dirk Staehle

The athors use OpNet simulations to determine the maximum number of calls in IEEE 802.11b,g,e networks. It's a week paper but is so close to our research area that makes it a very interesting reading. I must remember to include references to G711 and G729 codecs in our article.

Multicast Routing in Wireless Mesh Networks: Minimum Cost Trees or Shortest Path Trees

Uyen Trang Nguyen and Jin Xu

The authors present different techniques to build trees for multicast in wireless mesh networks.
SPT: Shortest Path Tree -> The one used on the Internet
MCT: Minimum Cost Tree
MST: Minimum Steiner trees as in wired networks.
MNT: Minimum Number of Transmissions for wireless networks. It accounts for the fact that a wireless transmission can reach various nodes.

The authors conclude that the SPT is better for various reasons. However, it seems to me that MNT should present numerous advantages such as reduced contention and collision. And it definetely present battery saving benefits.

TCP Throughput Enhancement over Wireless Mesh Networks

Li-Ping Tung, Wei-Kuan Shih, Te-Chung Cho and Yeali S. Sun

The article explains the hidden and exposed terminal problems. Using simulations, the authors relate this two effects to tcp performance. Finally, a channel assignment algorithm is proposed that optimizes TCP performance.

On Extending IMS Services to WLANs

Ahmed Hasswa* Abd-Elhamid Taha† Hossam Hassanein*

A proposal to integrate WLAN and IMS using AS. I don't see the point in proposing an alternative to the 3GPP integration.