International Journal of Ad Hoc & Sensor Wireless Networks ========================================================== Special Issue for MSN05 PAPER REVIEW FORM ----------------- Title: ACOS: An Area-based Collaborative Sleeping Protocol for Wireless Sensor Networks Author(s): Yanli Cai, Minglu Li, Wei Shu, and Min-You Wu Reviewer: Rick Ha Date To Be Returned: 10 Jan 06 ----------------------------------------------------------------------------- I. NUMERICAL RATING OF THE PAPER: --------------------------------------------------------------------------- Rating Category Your Rating Scale Definition --------------------------------------------------------------------------- Level of 5=Excellent Reader Interest |-----| 4=Very good | 3 | 3=Good |-----| 2=Fair 1=Poor --------------------------------------------------------------------------- Evaluation of Work 5=Excellent work and a major contribution and Contribution |-----| 4=Good solid work of some importance | 3 | 3=Solid work but marginal contribution |-----| 2=Marginal work and very minor contribution 1=Very questionable work and contribution --------------------------------------------------------------------------- Originality 5=Highly original work Novelty |-----| 4=Contains an original contribution | 2 | 3=Somewhat original |-----| 2=Variation of a known concept 1=Complete lack of original ideas --------------------------------------------------------------------------- Practical Utility 5=Excellent |-----| 4=Very good | 2 | 3=Good |-----| 2=Fair 1=Poor --------------------------------------------------------------------------- Quality of 5=Very good Presentation |-----| 4=Basically well-written | 4 | 3=Readable |-----| 2=Needs considerable work 1=Unacceptably bad --------------------------------------------------------------------------- Technical 5=Very good Correctness |-----| 4=Good | 3 | 3=Flaws but easy to correct |-----| 2=Some flaws 1=Unacceptably bad --------------------------------------------------------------------------- Overall Rating 5=Strong accept (very good quality) (could be .5) |-----| 4=Accept (good quality) | 3 | 3=Accept if room (marginal quality) |-----| 2=Likely reject (low quality) 1=Definitely reject (has no merit) --------------------------------------------------------------------------- II. SPECIFIC COMMENTS & SUGGESTIONS (to be made available to the author(s)): ------------------------------------ One of the fundamental issues with wireless sensor network coverage the authors did not mention is that coverage redundancy comes at a price. With sensor nodes currently available on the market costing well over $100 USD each, providing redundant coverage is a very expensive option. Even with the per unit price expected to drop to pennies in the future (if ever), a perhaps better and more economical solution is to simply add more battery power to each node. In this way, we can avoid the extra communication and processing overhead in managing the sleep schedules. The authors should at least provide such a cost comparison and design merits between increased node deployment vs. increased initial battery supply. While the authors concentrated on coverage issues, they seem to make the underlying assumption that the active nodes would somehow form a connected network. For this to happen, the sensor network has to be densely connected made possible either by long-range communication transceivers at each node or through dense deployment of the nodes. Both of these options would introduce additional considerations such as high transmission power, increased control overhead and cost. On the other hand, even if the transceiver remains in idle listening mode and does not transmit anything, its energy consumption is twice of that of the sensing unit according to the Mica2 specifications. Therefore, further energy savings can be achieved if the transceiver is allowed to follow a sleep cycle of its own that is optimized according to network traffic characteristics. It is important for the authors to address these issues regarding coverage and connectivity, and the authors may refer to works such as G. Xing et al in ACM Trans. Sensor Networks and Y. Zou at al in IEEE Trans. Computers on integrated approaches to jointly optimize coverage and connectivity. The simulation results under the selected parameters are not enough to demonstrate the applicability and scalability of the proposed approach to other usage scenarios. There are a number of messages defined in the proposed protocol. The authors are encouraged to use a table to list and describe them for a better presentation. What is the simulation environment? What simulation tools did the authors use? In terms of literary presentation, the paper is generally well-written. The reviewer did note the following blemishes: - Watch for the use of the article "the" throughout the paper. Sometimes it is not necessary to include "the" before a noun. - Page 2, Paragraph 1, "...but need further..." - Section 3.1, the authors need to define "r" before using it in bullet #2. - Section 5.3.2, Paragragh 1, "...replace any failed nodes..." III. CONFIDENTIAL COMMENTS (IF ANY) to be withheld from the author(s): ------------------------------------ Comments given under THIS item are for the EDITORS ONLY (to be withheld from the authors).