SUMMARYSystem level design considerations for high altitude platforms operating in the mm-wave bands are examined. Propagation e!ects in these bands are outlined, followed by a brief introduction to di!erent platform scenarios. Ground-based and platform-based "xed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The e!ects on performance of platform displacement from its desired location with both "xed and steerable antennas are also examined. It is shown that steerable antennas are of most use when "xed stations are immediately below the platform, with no bene"t for "xed stations on the edge of coverage. The bandwidths required to serve several tra$c distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The e!ects of temporal changes in the spatial tra$c distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes.

Background Although tuberculosis (TB) is a curable disease, treatment is complex and prolonged, requiring considerable commitment from patients. This study aimed to understand the common perspectives of TB patients across Brazil, Russia, India, China, and South Africa throughout their disease journey, including the emotional, psychological, and practical challenges that patients and their families face. Methods This qualitative market research study was conducted between July 2020 and February 2021. Eight TB patients from each country (n = 40) completed health questionnaires, video/telephone interviews, and diaries regarding their experiences of TB. Additionally, 52 household members were interviewed. Patients at different stages of their TB treatment journey, from a range of socioeconomic groups, with or without TB risk factors were sought. Anonymized data underwent triangulation and thematic analysis by iterative coding of statements. Results The sample included 23 men and 17 women aged 13–60 years old, with risk factors for TB reported by 23/40 patients. Although patients were from different countries and cultural backgrounds, experiencing diverse health system contexts, five themes emerged as common across the sample. 1) Economic hardship from loss of income and medical/travel expenses. 2) Widespread stigma, delaying presentation and deeply affecting patients’ emotional wellbeing. 3) TB and HIV co-infection was particularly challenging, but increased TB awareness and accelerated diagnosis. 4) Disruption to family life strained relationships and increased patients’ feelings of isolation and loneliness. 5) The COVID-19 pandemic made it easier for TB patients to keep their condition private, but disrupted access to services. Conclusions Despite disparate cultural, socio-economic, and systemic contexts across countries, TB patients experience common challenges. A robust examination of the needs of individual patients and their families is required to improve the patient experience, encourage adherence, and promote cure, given the limitations of current treatment.

This paper proposes a novel analytical approach to analyse the queuing delay and medium access distribution of CSMA-CA protocols over Multihop Personal Area Networks (MPANs). The proposed approach considers a general case without restrictions on the topology, traffic generation patterns or multipath routing policy and accounts for heterogeneous traffic patterns, all possible packet loss scenarios and the effect of the length of the back-off on the channel assessment. This work uses statistical theorems to derive the Moment Generating Function (MGF) of the time required to service a packet, then uses this function as a service distribution in a GI/G/1 queuing model to derive the inter-departure and total queuing delays. From these functions the end-to-end delay, jitter, throughput and failure transmission probability over a path are derived. Besides determination of these metrics, this study exploits the statistical features of the MGF to determine the rare event probability of the service function. The proposed approach is exemplified using the state-of-the-art IEEE 802.15.4 CSMA-CA protocol, and its accuracy is demonstrated through comparison with simulations.Index Terms-Queuing delay, medium access control, multihop, CSMA-CA, IEEE 802.15.4. 0018-9545 (c)

High Altitude Platforms may offer high spectrum efficiency by deploying multi-beam, multi-cell communications networks. The properties of the antennas carried by the HAP payload are key to the effective exploitation of these benefits. This paper compares different models for the antenna sidelobe region and quantifies, in each case, the carrier to interference ratio for a 3 channel re-use plan. Networks of 121 and 313 cells are compared. We show how the ITU recommended pattern for the 47/48 GHz band leads to pessimistic results compared to an adapted pattern which fits that of measured data for an elliptic beam lens antenna. The method is then extended to consider other radiation patterns. Spectrum sharing issues are explored with reference to further ITU recommendations and comparison with measurement data. Finally, an ITU type cellular layout which uses the same antenna for each cell is compared to an alternative hexagonal layout where each cell has equal size.

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IEEE 802.15.4 is the first recognized standard that can replace the large number of proprietary PHY and MAC protocols for Low Rate Wireless Personal Area Networks (LRWPANs). To balance the conflicting demands of low-delay data delivery and consumed energy, this standard employs CSMA-CA as the multiple-access scheme. However, a critical study of this protocol's operation under different conditions shows room for improvement. In this paper we propose two algorithms to improve the performance of this standard: time-based frame aggregation and selective frames. We evaluate these proposals under different conditions using performance indices including delay, throughput, and collision rate. Our simulation results together with analytical expressions from related work demonstrate the benefits of our proposed ideas.

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