| 1. |
- Eriksson, Jonas, et al.
(author)
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On Coding of Scheduling Information in OFDM
- 2009
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In: Proceedings of the 69th IEEE Vehicular Technology Conference. - 9781424425174
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Conference paper (peer-reviewed)abstract
- Control signaling strategies for scheduling information in cellular OFDM systems are studied. A single-cell multiuser system model is formulated that provides system capacity estimates accounting for the signaling overhead. Different scheduling granularities are considered, including the one used in the specifications for the 3G Long Term Evolution (LTE). A greedy scheduling method is assumed, where each resource is assigned to the user for which it can support the highest number of bits. The simulation results indicate that the cost of control signaling does not outweigh the scheduling gain, when compared with a simple round-robin scheme that does not need signaling of scheduling information. Furthermore, in the studied scenario, joint coding and signaling of scheduling information over all selected users is found to be superior to separate coding and signaling for each user. The results also indicate that the scheduling granularity used for LTE provides better performance than the full granularity.
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| 2. |
- Gunnarsson, Fredrik, et al.
(author)
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Admission Control in Cellular Radio Systems Based on Relative Load Estimates
- 2001
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In: Proceedings of the Third Conference on Computer Science and Systems Engineering. - Linköping : Linköping University Electronic Press. ; , s. 163-168
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Conference paper (other academic/artistic)abstract
- When operating a cellular radio system nearly at full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. The core idea in this work is to predict the relative load of the system, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. This provide an interesting alternative to algorithms based on hard capacity, which might be utilizing the resources inefficiently in order to be robust. The proposed uplink admission control algorithm utilizes measurements readily available in the system. Simulations indicate performance improvements. Furthermore, multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate.
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| 3. |
- Gunnarsson, Fredrik, et al.
(author)
-
Combining of Power Control Commands During Soft Handover in WCDMA
- 2003
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In: Proceedings of the 14th IEEE Personal, Indoor and Mobile Radio Communications. - 0780378229 ; , s. 1757-1760 vol.2
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Conference paper (peer-reviewed)abstract
- This paper discusses the TPC detection performance in soft handover in WCDMA. A simple TPC commands combining method is evaluated and an improved TPC combining method is proposed. Results show that although the simple combining method fulfills the 3GPP requirements, it does not perform well from the system performance perspective. The proposed combining method significantly improves the system performance.
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| 4. |
- Gunnarsson, Fredrik, et al.
(author)
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Performance Evaluation of Activity-Based Uplink Load Estimates in WCDMA
- 2004
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In: Proceedings of thee IEEE Global Telecommunications Conference 2004. - 0780387945
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Conference paper (peer-reviewed)abstract
- Activity-based uplink load estimation is considered for WCDMA. By taking the user activity explicitly into account, the method is suitable for a scenario where services with very different activity levels use the same RAB. Scenarios with different mixes of email and MMS (multimedia messaging service) traffic are considered. Simulations indicate that the method provides good accuracy in situations where methods without activity estimation may overestimate the uplink load with about 3 dB.
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| 5. |
- Gunnarsson, Fredrik, et al.
(author)
-
Transmit Power Control Time Delay Compensation in a Wireless Communications System
- 2002
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Patent (pop. science, debate, etc.)abstract
- The present invention compensates for transmit power control time delays between a radio transmitter and receiver that adversely affect the transmit power control process. A time delay associated with a power control loop is compensated for by adjusting a detected signal quality value of a received signal, e.g., signal-to-interference ratio (SIR), based on one or more previous power control commands already sent but whose effect has not yet been experienced. Because the determined signal quality value of the received signal is adjusted based on one or more power control commands already sent but yet to take effect, the transmit power level control command is appropriately determined so that it also takes into account a power control loop time delay. The delay compensation value may be determined based on the output power of a single, previously generated transmit power control command, or on plural previously generated transmit power control commands, depending upon the length of the time delay. If the adjusted signal quality parameter exceeds the target signal quality parametery the generated power control command directs a decrease in transmit power, and the compensation factor causes a decrease in the subsequently determined signal quality parameter. If the adjusted signal quality parameter is less than the target signal quality parameter, the generated power control command directs an increase in transmit power, and the compensation factor causes an increase in the subsequently determined signal quality parameter.
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| 6. |
- Gunnarsson, Fredrik, et al.
(author)
-
Uplink Admission Control in WCDMA Based on Relative Load Estimates
- 2002
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In: Proceedings of the 2002 IEEE International Conference on Communications. - Linköping : Linköping University Electronic Press. - 0780374002 ; , s. 3091-3095 vol.5
-
Conference paper (peer-reviewed)abstract
- When operating a cellular radio system at nearly full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. Prior art includes algorithms which are limiting the number of users or the uplink interference per cell. Both are known to yield roughly the same performance, but the former is difficult to configure, and the latter is based on a quantity, which is hard to measure accurately. The core idea in this work is to predict the relative load of the system directly, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. The proposed uplink relative load estimate is focused on WCDMA. It utilizes measurements readily available in that system, either periodically scheduled or from handover events. Multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate. Simulations indicate that the admission control operates satisfactory in different traffic situations with a universal parameter setting. Furthermore, the reporting overhead with periodical measurements can be avoided, since handover event-driven measurements yield roughly the same performance.
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| 7. |
- Gunnarsson, Fredrik, et al.
(author)
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Uplink Transmission Timing in WCDMA
- 2003
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In: Proceedings of the 58th IEEE Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780379543 ; , s. 1688-1692 vol.3
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Conference paper (peer-reviewed)abstract
- In wireless network uplink communications, there is a trade off between transmission coordination to avoid overload situations, and distributed transmission decisions to adapt to fast channel variations. Here, uplink transmission timing (UTT) is proposed as a scheme to allow some load control support, while transmitting mainly when the channel is favorable. It utilizes channel state feedback in the form of power control commands, which already are available in the system. Simulations illustrate the transmission timing behavior, and also indicate that UTT is a power and intercell interference efficient scheme to transport data compared to traditional dedicated channels with continuous transmissions and to schemes where transmission decisions are random.
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| 8. |
- Lundevall, Magnus, et al.
(author)
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Streaming Applications Over HSDPA in Mixed Service Scenarios
- 2004
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In: Proceedings of the 60th IEEE Vehicular Technology Conference. - 0780385217 ; , s. 841-845
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Conference paper (peer-reviewed)abstract
- High-speed downlink packet access (HSDPA) is included in release 5 of the WCDMA specifications to increase downlink capacity and bitrates. This paper considers performance aspects of streaming applications over HSDPA in a mixed streaming and best-effort service scenario. Different scheduling algorithms are evaluated with the aim of providing sufficient quality-of-service for streaming. The simulation results show that reasonable streaming performance can be achieved without service differentiation if a somewhat fair scheduler is used, and that a streaming-aware scheduler further can protect streaming quality-of-service in high load conditions.
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| 9. |
- Moosavi, Reza, 1982-, et al.
(author)
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Comparison of Strategies for Signaling of Scheduling Assignments in Wireless OFDMA
- 2010
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In: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 59:9, s. 4527-4542
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Journal article (peer-reviewed)abstract
- This paper considers transmission of scheduling information in OFDMA-based cellular communication systems such as 3GPP long-term evolution (LTE). These systems provide efficient usage of radio resources by allowing users to be scheduled dynamically in both frequency and time. This requires considerable amounts of scheduling information to be sent to the users. The paper compares two basic transmission strategies: transmitting a separate scheduling message to each user versus broadcasting a joint scheduling message to all users. Different scheduling granularities are considered, as well as different scheduling algorithms. The schemes are evaluated in the context of the LTE downlink using multiuser system simulations, assuming a full-buffer situation. The results show that separate transmission of the scheduling information requires a slightly lower overhead than joint broadcasting, when proportional fair scheduling is employed and the users are spread out over the cell area. The results also indicate that the scheduling granularity standardized for LTE provides a good trade-off between scheduling granularity and overhead.
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| 10. |
- Sundström, Johan, Professor, 1971-, et al.
(author)
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Risk factors for subarachnoid haemorrhage : a nationwide cohort of 950 000 adults
- 2019
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In: International Journal of Epidemiology. - : Oxford University Press. - 0300-5771 .- 1464-3685. ; 48:6, s. 2018-2025
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Subarachnoid haemorrhage (SAH) is a devastating disease, with high mortality rate and substantial disability among survivors. Its causes are poorly understood. We aimed to investigate risk factors for SAH using a novel nationwide cohort consortium.METHODS: We obtained individual participant data of 949 683 persons (330 334 women) between 25 and 90 years old, with no history of SAH at baseline, from 21 population-based cohorts. Outcomes were obtained from the Swedish Patient and Causes of Death Registries.RESULTS: During 13 704 959 person-years of follow-up, 2659 cases of first-ever fatal or non-fatal SAH occurred, with an age-standardized incidence rate of 9.0 [95% confidence interval (CI) (7.4-10.6)/100 000 person-years] in men and 13.8 [(11.4-16.2)/100 000 person-years] in women. The incidence rate increased exponentially with higher age. In multivariable-adjusted Poisson models, marked sex interactions for current smoking and body mass index (BMI) were observed. Current smoking conferred a rate ratio (RR) of 2.24 (95% CI 1.95-2.57) in women and 1.62 (1.47-1.79) in men. One standard deviation higher BMI was associated with an RR of 0.86 (0.81-0.92) in women and 1.02 (0.96-1.08) in men. Higher blood pressure and lower education level were also associated with higher risk of SAH.CONCLUSIONS: The risk of SAH is 45% higher in women than in men, with substantial sex differences in risk factor strengths. In particular, a markedly stronger adverse effect of smoking in women may motivate targeted public health initiatives.
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