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Backgroud The purpose of this study was to evaluate the clinical usefulness of open-door laminoplasty using lateral mass anchoring screws and nonabsorbable sutures (ODLLM) for multilevel cervical myelopathy. Methods We retrospectively studied 30 patients who underwent ODLLM. Clinical evaluations were performed using a visual analog scale (VAS), Japanese Orthopaedic Association (JOA) score, and Neck Disability Index (NDI) preoperatively, at 1 year postoperatively, and at the last follow-up. Radiographic evaluation was done using cervical spine radiographs to measure changes in the lordotic angle and range of motion (ROM) preoperatively, at 1 year postoperatively, and at the last follow-up and computed tomography at 1 year postoperatively to measure the opening angle and anteroposterior diameter of the spinal canal. Results Significant improvement in VAS, JOA, and NDI was seen overall at 1 year after operation. However, there was no significant difference between 1 year after operation and the last follow-up. There were no significant changes in the lordotic angle and neck ROM. The mean opening angle of the opened lamina was measured as 39.04°. The mean anteroposterior diameter was significantly increased from 7.51 ± 1.79 mm before surgery to 13.98 ± 1.80 mm at 1 year of operation. Complications such as laminar reclosure and screw loosening were not observed in all cases. Conclusions The ODLLM was technically easy to perform and showed good results comparable to those of conventional techniques. It can be suggested that ODLLM is an appropriate treatment option for multilevel cervical myelopathy.

Objective Minimal data exist regarding non-operative management of suspected pseudarthrosis after pedicle subtraction osteotomy (PSO). This study reports radiographic and clinical outcomes of non-operative management for post-PSO pseudarthrosis at a minimum 5 years post-detection. Methods Nineteen consecutive patients with implant breakage indicating probable pseudarthrosis after PSO surgery (13 women/ six men; mean age at surgery, 58 years) without severe pain and disability were treated with non-operative management (mean follow-up, 5.8 years; range, 5–10 years). Non-operative management included medication, intermittent brace wearing and avoidance of excessive back strain. Radiographic and clinical outcomes analysis was performed. Results Sagittal vertical axis (SVA), proximal junctional angle, thoracic kyphosis achieved by a PSO were maintained after detection of pseudarthrosis through ultimate follow-up. Lumbar lordosis and PSO angle decreased at final follow-up. There was no significant change in Oswestry Disability Index (ODI) scores and Scoliosis Research Society (SRS) total score, or subscales of pain, self-image, function, satisfaction and mental health between detection of pseudarthrosis and ultimate follow-up. SVA greater than 11 cm showed poorer ODI and SRS total score, as well as the pain, self-image, and function subscales (p

A land mobile satellite (LMS) system is helpful to various fields such as commercial and military applications thanks to its coverage, flexibility, broadcast capability, costs independent on the distance and easy deployment. Besides, since the low data and voice services can be provided via the hand-held terminal, the availability of the LMS system has been increasing. For deep shadowing and non-line-of-sight conditions in the LMS environment, hybrid satellite-terrestrial relay networks (HSTRNs) are widely used. However, the robust link adaptation level would be selected in the LMS environment to prevent the performance degradation of transmission control protocol (TCP), resulting in reducing the spectral efficiency. In this paper, we propose a reliable file transfer framework with application layer forward error correction (AL-FEC) in the LMS network. In particular, we propose a target bit error rate (BER) selection algorithm in the proposed framework to select the permitted target BER much loosely for the AL-FEC system because it is a rate-based system and provides the full reliability of the file transfer. In this paper, the cross-layer design is also considered for the proposed file transfer framework with AL-FEC and the BER selection algorithm. We also theoretically derive the goodput and the spectral efficiency by the given BER of the LMS channel to demonstrate the effectiveness of the proposed framework. The results of performance evaluation show that the required signal to noise ratio of the proposed framework can be reduced with satisfying the goodput requirement of the system as compared with the TCP solution. Furthermore, the link adaptation with the proposed target BER selection algorithm in the proposed framework can reduce the bandwidth needed to send the data in the satellite link, the number of terrestrial relays in the HSTRN, and the transmission power in the ground station while guaranteeing the goodput requirement.

Background The purpose of this study was to compare the results of arthroscopically guided suprascapular nerve block (SSNB) and blinded axillary nerve block with those of blinded SSNB in terms of postoperative pain and satisfaction within the first 48 hours after arthroscopic rotator cuff repair. Methods Forty patients who underwent arthroscopic rotator cuff repair for medium-sized full thickness rotator cuff tears were included in this study. Among them, 20 patients were randomly assigned to group 1 and preemptively underwent blinded SSNB and axillary nerve block of 10 mL 0.25% ropivacaine and received arthroscopically guided SSNB with 10 mL of 0.25% ropivacaine. The other 20 patients were assigned to group 2 and received blinded SSNB with 10 mL of 0.25% ropivacaine. Visual analog scale (VAS) score for pain and patient satisfaction score were assessed 4, 8, 12, 24, 36, and 48 hours postoperatively. Results The mean VAS score for pain was significantly lower 4, 8, 12, 24, 36, and 48 hours postoperatively in group 1 (group 1 vs. group 2; 5.2 vs. 7.4, 4.1 vs. 6.1, 3.0 vs. 5.1, 2.1 vs. 4.2, 0.9 vs. 3.9, and 1.3 vs. 3.3, respectively). The mean patient satisfaction score was significantly higher at postoperative 4, 8, 12, 24, 36, and 48 hours in group 1 (group 1 vs. group 2; 6.7 vs. 3.9, 7.4 vs. 5.1, 8.8 vs. 5.9, 9.2 vs. 6.7, 9.5 vs. 6.9, and 9.0 vs. 7.2, respectively). Conclusions Arthroscopically guided SSNB and blinded axillary nerve block in arthroscopic rotator cuff repair for medium-sized rotator cuff tears provided more improvement in VAS for pain and greater patient satisfaction in the first 48 postoperative hours than blinded SSNB.

Objective To evaluate and compare the clinical and radiographic features of 25 patients with infectious spondylitis treated with anterior debridement and reconstruction using autogenous bone grafts vs. a metal cage with allogenic bone grafts. Methods The study analyzed 25 patients diagnosed with infectious thoracolumbar spondylitis who underwent anterior radical debridement and reconstruction. Autogenous bone grafts were used in 13 patients (group 1), and a metal cage with allogenic bone grafts was used in 12 patients (group 2). Clinical outcomes were assessed by the visual analogue scale (VAS) scores and neurological status. Additionally, the serological results and the radiographic results using the sagittal Cobb angle were compared. Fusion was evaluated by computed tomography (CT) imaging at 24 months postoperatively. Results Both groups showed a significant decrease in the postoperative mean VAS scores; however, only, group 1 patients showed a significantly higher VAS score than group 2 patients, 1 month postoperatively (p=0.002). The postoperative neurological status significantly improved. Elevated C-reactive protein levels and erythrocyte sedimentation rate values returned to normal limits at the 2-year follow-up without recurrent infection. No significant intergroup difference was observed in Cobb angle. Bony fusion was confirmed in all patients at CT 24 months postoperatively. Conclusion Although the use of a metal cage with allogenic bone grafts for anterior column reconstruction remains controversial, our results suggest that it can be considered as an effective treatment of option for anterior column reconstruction in patients with infectious spondylitis.

Guaranteeing quality of service over a multihop wireless network is difficult because end-to-end (ETE) delay is accumulated at each hop in a multihop flow. Recently, research has been conducted on network coding (NC) schemes as an alternative mechanism to significantly increase the utilization of valuable resources in multihop wireless networks. This paper proposes a new section-based joint NC and scheduling scheme that can reduce ETE delay and enhance resource efficiency in a multihop wireless network. Next, this paper derives the average ETE delay of the proposed scheme and simulates a TDMA network where the proposed scheme is deployed. Finally, this paper compares the performance of the proposed scheme with that of the conventional sequential scheduling scheme. From the performance analysis and simulation results, the proposed scheme gives more delay-and energy-efficient slot assignments even if the NC operation is applied, resulting in a use of fewer network resources and a reduction in ETE delay.

Background Posterior lumbar surgery can lead to damage on paraspinal muscles. Objective Our study aimed to examine the recovery in the denervated paraspinal muscles by posterior lumbar surgery and to determine that of improvement in the lower back pain (LBP). Methods Depending on surgical treatments, the patients were divided into two groups: The group I (interspinous implantation with decompression) and II (posterior lumbar interbody fusion with decompression). The paraspinal mapping score was recorded for individual muscle. Results In the group I, there was reinnervation in the denervated multifidus and erector spinae at the upper, surgical and lower levels at 12 months. In the group II, there was reinnervation in the denervated erector spinae at the upper, surgical and lower levels at 12 months. There was significant aggravation in the LBP in both groups at immediate postoperative. But there was significant improvement in it at 6 months in the group I and at 12 months in the group II. Conclusion There was reinnervation in not only denervated multifidus and erector spinae at 12 months following interspinous ligament stabilization but also in denervated erector spinae at 12 months following pedicle screw fixation with fusion.

Introduction We analyzed the location of femoral and tibial tunnels by three-dimensional (3D) CT reconstruction images after modified transtibial single bundle (SB) anterior cruciate ligament (ACL) reconstruction, creating a femoral tunnel with varus and internal rotation of the tibia. Material and methods Data from 50 patients (50 knees) analyzed by 3D CT after modified transtibial SB ACL reconstructions were evaluated. 3D CT images were analyzed according to the quadrant method by Bernard at the femur and the technique of Forsythe at the tibia. Results The mean distance of the femoral tunnel center locations parallel to the Blumensaat's line was 29.6% ± 1.9% along line t measured from the posterior condylar surface. The mean distances perpendicular to the Blumensaat's line were 37.9% ± 2.5% along line h measured from the Blumensaat's line. At the tibia, the mean anterior-to-posterior distance for the tunnel center location was 37.8% ± 1.2% and the mean medial-to-lateral distance was 50.4% ± 0.9%. Discussion The femoral and tibial tunnels after modified transtibial SB ACL reconstruction creating a femoral tunnel with varus and internal rotation of the tibia (figure-of-4 position) were located between the anatomical anteromedial and posterolateral footprints.

This study investigated the changes in the growth and phenotype of human degenerated intervertebral disc cells depending on the frequency of subculture and the growth factors effects in vitro monolayer culture system. The twice passaged nucleus pulposus (NP) cells were replated six well plates at a density 1×104 cells/cm2. The replated NP cells were divided into four subgroups: no treatment (control group), the treatment of 10 ng/mL transforming growth factor (TGF)-β1 (TGF group), treatment of 5 ng/mL basic fibroblast growth factor (bFGF, FGF group), and treatment of TGF-β plus bFGF (TGF/FGF group). Analyses of proliferation, morphology, histological and reverse transcriptase — polymerase chain reaction (RT-PCR) were made at different time point. The NP cells gradually showed a fibroblast-like spindle shape from their irregular, polygonal shape while undergoing the third time of subculture. The cell proliferation was the highest at the second subculture time. On RT-PCR, the type II collagen expression was gradually decreased and almost unexpressed at the third subculture, but the type I collagen expression was gradually increased in the NP cells. The expression of proteoglycan was gradually decreased in NP cells and it was almost unexpressed at the third time of subculture. FGF can stimulate NP cell proliferation and TGF-β showed increase collagen type II and aggrecan synthesis, and the combination of TGF and FGF appeared both effects of proliferation and extracellular matrix (ECM) synthesis on the NP metabolism. To obtain a great number of cells using a small frequency of subculture and to increase the ECM synthesis, new culture methods based on growth factors or mechanical stimulation must be considered.

This paper introduces waiting time based periodic packet discard policy for frame based scheduler. This policy can be used with conventional packet discard policy or buffer management schemes, such as drop-tail or random early detection. Proposed discard policy discards packets, which are stayed in the buffer longer than threshold, at every period of scheduling. This decision of discard is based on waiting time of packet. In this paper, mathematical analysis is performed with situation of network congestion. Also, the simulation is performed to evaluate the performance of proposed discard policy. In the result, proposed discard policy can limit queuing delay by threshold. Also, if the packet discard is performed before scheduling and threshold is set with smaller value than frame length, it can limit the throughput of traffic.

Background Recurrence of glenohumeral dislocation after arthroscopic Bankart repair can be associated with a large osseous defect in the posterosuperior part of the humeral head. Our hypothesis is that remplissage is more effective to prevent recurrence of glenohumeral instability without a severe motion deficit. Methods Engaging Hill-Sachs lesions were observed in 48 of 737 patients (6.5%). Twenty-four patients underwent arthroscopic Bankart repair combined with remplissage (group I) and the other 24 patients underwent arthroscopic Bankart repair alone (group II). Clinical outcomes were prospectively evaluated by assessing the range of motion. Complications, recurrence rates, and functional results were assessed utilizing the American Shoulder and Elbow Surgeons (ASES) score, Rowe score, and the Korean Shoulder Score for Instability (KSSI) score. Capsulotenodesis healing after remplissage was evaluated with magnetic resonance imaging. Results The average ASES, Rowe, and KSSI scores were statistically significantly higher in group I than group II. The frequency of recurrence was statistically significantly higher in group II. The average loss in external rotation measured with the arm positioned at the side of the trunk was greater in group II and that in abduction was also higher in group II. Conclusions Compared to single arthroscopic Bankart repair, the remplissage procedure combined with arthroscopic Bankart repair was more effective to prevent the recurrence of anterior shoulder instability without significant impact on shoulder mobility in patients who had huge Hill-Sachs lesions.

Background To the best of our knowledge, there have been no reports on the points at which the denervated multifidus and erector spinae muscles become reinnervated after pedicle screw fixation and posterior fusion in patients with lumbar degenerative diseases. Our study was designed to confirm reinnervation of denervated paraspinal muscles following pedicle screw fixation and posterior fusion and to confirm alleviation of the patients’ lower back pain (LBP). Methods In this prospective study, we enrolled 67 patients who had undergone pedicle screw fixation and posterior fusion. The surgery had alleviated their leg pain, but the patients complained of LBP at the L3-5 level 3 months after the surgery. The patients were divided into two groups (I and II) according to the level at which pain was experienced. Paraspinal mapping scores were recorded preoperatively and 3, 6, 12, and 18 months postoperatively. Oswestry Disability Index and visual analogue scale scores were determined. Regression analyses using a general linear model and a mixed model were performed. Results Pedicle screw fixation and posterior fusion significantly denervated the multifidus and erector spinae not only in the surgical segment, but also in adjacent segments. Group I patients displayed reinnervation in the denervated erector spinae and multifidus muscles at 12 and 18 months, respectively. In contrast, group II showed reinnervation only in of the denervated erector spinae of the upper segment at 18 months, with no other areas of reinnervation. Postoperative LBP was significantly diminished at 12 months in group I and at 18 months in group II. There was also significantly less LBP at 6 months (prior to reinnervation of the paraspinal muscles). Conclusions The denervated multifidus and erector spinae muscles at L4–5, which had been denervated using pedicle screw fixation and posterior fusion, were significantly reinnervated at 18 months postoperatively, whereas patients with denervation at L3–5 had only a tendency to be reinnervated at follow-up. Postoperative LBP in these patients was significantly diminished at the follow-up visits.

This paper introduces two multi-hop delay factors which can be caused by conventional TDMA scheduling; queueing delay and delay by random link scheduling, and proposes a new sequential scheduling scheme to resolve these two factors. We also simulate the TDMA network with the proposed link scheduling scheme and compare it with conventional(random) link scheduling scheme in terms of end-to-end packet transmission delay. From the simulation results, the more the average hop distance increases, the more the difference of the delay performance of both scheduling schemes increases. When the average number of hops is 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 22%, 36%, 48%, and 55% respectively when compared to the random scheduling scheme.

This letter proposes a new distributed scheduling scheme combined with routing to support the quality of service of realtime applications in wireless mesh networks. Next, this letter drives average end-to-end delay of the proposed scheduling scheme that sequentially schedules the slots on a path. Finally, this letter simulates the time division multiple access network for performance comparison. From the simulation results, when the average number of hops is 2.02, 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 28%, 10%, 17%, 27%, and 30%, respectively, compared to the conventional random scheduling scheme.

Mucoid degeneration of the anterior cruciate ligament (ACL) is a little-known entity. The aim of this study was to detail the clinical, radiological, arthroscopic and pathological findings of this condition and to report clinical outcomes following arthroscopic partial excision of the ACL. Between 1999 and 2009, 80 knees in 78 patients were diagnosed as having mucoid degeneration of the ACL based on MRI and clinical findings, and subsequently underwent arthroscopic treatment. Of these, 68 knees in 66 patients, with a median age of 51 years (range, 35–75 years), were followed-up for at least one year. All patients had insidious onset of knee pain, while 56 knees (82 %) had associated extension deficits and 36 knees (53 %) had restricted flexion. MRI findings typically showed diffuse thickening and increased signal intensity of the ACL. Arthroscopic examination revealed notch impingement and bulging of hypertrophied ACL into lateral compartments. Associated lesions included meniscal tears in 33 knees and chondral lesions of at least Outerbridge grade 2 in 56 knees. All knees underwent arthroscopic partial excision of the hypertrophied ACL, with three undergoing preoperative and 30 undergoing concomitant meniscectomies. Pain relief was achieved in 58 of 62 knees (94 %) following partial excision of the ACL. Extension deficits were normalized in 49 of 56 knees (88 %), and restricted flexion was normalized in 33 of 36 affected knees (92 %). Four knees of four patients had postoperative symptoms of anterior instability. Pain and limitation of motion due to mucoid degeneration of the ACL can be improved by arthroscopic partial excision of the ACL with or without notchplasty. However, one potential complication is the development of postoperative symptoms of anterior instability. Retrospective study, Level IV.

Ninety-nine patient outcomes were evaluated and compared prospectively.Sixty-nine patients with full-thickness tears of the upper subscapularis tendon underwent arthroscopicrepair (group I) and thirty patients underwent simple debridement (group II) between May 2003 andOctober 2007. In all patients, the tear was localized to the superior one third of the upper subscapularistendon. The results of the treatment were assessed by evaluating the UCLA, ASES, and VAS for pain andinternal rotation strength scores before and after the operation.

Purpose: To evaluate the usefulness of arthroscopic decompression and miniopen repair that was related with large and massive sized full thickness rotator cuff tear and assess clinical result. Materials and Methods: Twenthy-nine cases of miniopen repaired full thickness tear of rotator cuffs that arthroscopically decompressed were studied. From October 1998 to December 2004 we have analysed 29 repairs of large and massive sized FTRCT, the average age 44 () years old, mean follow-up was 34 () months. We analyzed the results statistically by paired t-test. Results: Postoperative VAS of pain improved average 7.0 to 1.7, UCLA score improved 13.7 to 31.9, ADL improved 11.3 to 25.3 respectively (all, P

Background This study aims to compare the surgical outcomes of open reduction and internal fixation (ORIF) and minimally invasive plate osteosynthesis (MIPO) using a screw compression method in simple humeral shaft fractures. Methods This retrospective study was performed with 50 patients who had surgical interventions for the treatment of simple humeral shaft fractures and had follow-ups of at least 12 months in Ulsan University Hospital between August 2008 and June 2015. Group 1 included 23 patients treated with ORIF and group 2 included 27 patients treated with the MIPO technique using a locking screw plate. The time to clinical/radiographic union, the joint range of motion (ROM), and function were evaluated. Results The average time to clinical/radiographic bone union was shorter in group 2 (12.0 ± 3.7 weeks/14.8 ± 2.0 weeks in group 1 and 9.4 ± 1.3 weeks/12.0 ± 3.3 weeks in group 2; p = 0.022/p = 0.034). Shoulder and elbow joint function evaluated by joint ROM and visual analogue scale (VAS), Korean Shoulder Elbow Society (KSS), American Shoulder and Elbow Surgeons (ASES), and the University of California at Los Angeles (UCLA) scores was excellent in both groups. On the average shoulder ROM at 12 months after the operation, group 1 had forward elevation of 160°, external rotation of 30° in adduction and lumbar vertebra 10 level in internal rotation and group 2 had forward elevation of 170°, external rotation of 35° in adduction and lumbar vertebra 9 level in internal rotation. The mean VAS, KSS, ASES, and UCLA scores were 2.8, 87.0 ± 0.9, 89.4 ± 0.9, and 31.0 ± 1.4, respectively, in group 1 and 1.7, 89.1 ± 2.7, 91.0 ± 1.6, and 32.4 ± 3.2, respectively, in group 2. There were statistically significant intergroup differences in VAS score (p = 0.011). There were significantly less postoperative infections in group 2 (three cases, 10.7% in group 1 and 0 case in group 2; p = 0.041) although all of them were superficial infections and well-treated by an average 4-week course of antibiotics (range, 2 to 6 weeks). Conclusions MIPO using a screw compression method in simple humeral shaft fractures demonstrated superior efficacy to ORIF in terms of the time to clinical/radiographic union, pain score, and postoperative infection rate.

A converged satellite and terrestrial network (CSTN) can be used for globally unified networking in areas where there is no infrastructure. However, the different characteristics between a satellite network and a terrestrial network lead to researches on converged network architectures, data transmission methods, resource managements, and etc. In this paper, we deal with these research issues in terms of efficient routing of user data and the employment of routing protocols in the CSTNs. First, we suggest a network architecture for the selection of efficient routing path based on several design criteria. Then, we figure out issues and their solutions when a dynamic routing protocol is applied to the CSTNs. These issues are focused on the signaling process for connection setup and maintenance, resource allocation for a satellite link, and mobility management. We have shown that the CSTNs can achieve the efficient routing path selection, increase channel utilization, and decrease signaling overheads for the exchange of routing information by using the suggested solutions.

To improve reliability of packet transmission, wireless communication systems use appropriate retransmission schemes based on characteristics of each protocol layer. In each protocol layer, retransmission schemes operate without cooperation of other layers. However, to improve system performance over wireless channel, a retransmission scheme of each protocol layer can use information on other protocol layers. For this reason, the cross-layer retransmission schemes recently have been proposed. The cross-layer retransmission scheme that is an retransmission scheme combined with adaptive modulation and coding (AMC) scheme can improve average spectral efficiency by considering both wireless channel state and parameters of a retransmission scheme. However, conventional researches concentrate on improving system performance over wireless channel and the end-to-end performance is not considered. It may be difficult to find an appropriate cross-layer retransmission scheme and system parameters for each service class. Thus, the end-to-end performance should be analyzed to decide whether the cross-layer retransmission schemes and parameters are suitable for each service class. In this paper, we analyze the end-to-end performance of wireless communication system using a cross-layer retransmission scheme and evaluate the system performance such as spectral efficiency, packet error rate (PER), and end-to-end throughput on transport layer. From the evaluation results, it can be seen that the end-to-end throughput of the hybrid automatic repeat request (HARQ) scheme combined with AMC is superior to that of automatic repeat request (ARQ) combined with AMC.

We propose a new time division multiple access(TDMA)-based distributed scheduling scheme for timely multi-hop transmission of delay-sensitive information in wireless sensor networks(WSNs). We first introduce two multi-hop delay factors which can be caused by conventional TDMA scheduling; queueing delay and the delay by random link schedule. Next, this paper drives average end-to-end delay of the proposed scheduling scheme and the conventional scheduling scheme that randomly schedules the slots on the path. Finally, this paper simulates the TDMA network for the performance comparison. From the simulation results, when the average number of hops is 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 22%, 36%, 48%, and 55% respectively compared to the random scheduling scheme.

This paper proposes a new time division multiple access (TDMA) based multi-hop resource(slots) reservation protocol (TMRR) for tactical mobile adhoc networks (T-MANET). TMRR lets a node reserve the channel resource for multi-hop packet transmission in consecutive order, so that the packet transmission between a source node and a multi-hop away destination node is possible within a superframe. This paper evaluates the performance of the proposed protocol via OPNET simulation in terms of the average end-to-end delay and the average throughput in both static and mobile environments. And this paper compares it to that of the Evolutionary-TDMA (E-TDMA) which is a representative reservation-based medium access control (MAC) protocol considering node mobility in MANET. According to the simulation results of the single-hop scenarios, TMRR gives better packet throughput and delay performance than E-TDMA as the offered traffic is increased. For the multi-hop scenarios, the average end-to-end delay of TMRR nodes meets the multi-hop end-to-end delay requirements because a node can transmit the packets to a multi-hop away node within a superframe.

This paper proposes a new backoff algorithm to enhance both the delay and the throughput of the Distributed Coordination Function (DCF) in the IEEE 802.11 based wireless networks. The proposed algorithm, which is named as the Estimation-based Backoff Algorithm (EBA), observes the number of the idle slots during the backoff period in order to estimate the number of active nodes in the network. Especially, when the number of nodes or the amount of traffic dramatically varies, the proposed algorithm determines a more appropriate contention window based on the estimation algorithm. This paper evaluates the performance of the proposed EBA by using simulation, and it compares the EBA's performance with other backoff algorithms such as the binary exponential back-off (BEB), the exponential increase exponential decrease (EIED), the exponential increase linear decrease (EILD), the pause count backoff (PCB) and the history based adaptive backoff (HBAB). The simulation results show that the EBA outperforms the other backoff algorithms because it has better adaptability to the network load variation. By comparing the performance of the EBA to that of the BEB, which is defined in the IEEE 802.11, the EBA increases the network throughput by around 25%, and it decreases the mean packet delay by about 50% when the number of nodes is 70.

We propose two ALOHA-based Dynamic Framed Slotted ALOHA algorithms (DFSA) using tag estimation method (TEM), which estimates the number of tags around the reader, and dynamic slot allocation (DSA), which dynamically allocates the frame size for the number of tags. We compare the performance of the proposed DFSA with the conventional Framed Slotted ALOHA algorithm (FSA) using simulation. According to the analysis, two proposed DFSA algorithms show better performance than FSA algorithm regardless of the number of tags