CRAWDAD cu/antenna

Dataset of signal strength collected from 2.4 GHz directional antenna.We collected signal strength data to derive a parametric model for 2.4 GHz directional antennas.date/time of measurement start: 2007-08-16date/time of measurement end: 2008-03-07collection environment: As the demand for wireless networks grows, the research community continues to seek methods for improving network performance. One of the method for improving network throughput involves using directional antennas to increase signal gain and/or decrease interference. We collected signal strength data to derive a parametric model for (2.4 GHz) directional antennas.network configuration: We use two laptops, one receiver and one transmitter. Each is equipped with an Atheros-based MiniPCI-Express radio which is connected to an external antenna using a U.Fl to N pigtail adapter and a length of LMR-400 low-loss antenna cable. The receiver laptop is connected to a 7 dBi omnidirectional antenna on a tripod approximately two meters off the ground. The transmitter laptop is connected to the antenna we intend to model on a tripod 100 feet from the receiver and also two meters off the ground. The transmitter tripod features a geared triaxial head which allows precise rotation.data collection methodology: The transmitter radio is put in 802.11x ad hoc mode on the least congested channel. The transmitter’s ARP table is manually hacked to allow it to send UDP packets to a non-existent receiver. The receiver is put in monitor mode on the same channel and logs packets with tcpdump. Finally, both the receiver and transmitter must have antenna diversity disabled. With the equipment in place, the procedure is as follows: For each 5 degree position about the azimuth, send 500 un-acknowledged UDP packets. Without intervention otherwise, due to MAC-layer retransmits, each will be retried k times (where k is radio-vendor and/or driver implementation specific), resulting in k ∗ 500 measurements. During the experiment, the researchers themselves must be careful to stay well out of the near-field of the antennas and to move to the same location during runs (so that they, in effect, become a static part of the environment). If additional data is desired for a given location, multiple receivers can be used, provided the data from them is treated separately (as each unique path describes a unique environment).limitation: We were unable to aquire access to an anechoic chamber in time for this study, but would like to make use of one in future work, for even cleaner reference measurements. TracesetsrssTraceset of signal strength collected from 2.4 GHz directional antenna.file:cu-antenna-data-200905.tar.gzdescription: We collected signal strength data to derive a parametric model for 2.4 GHz directional antennas.measurement purpose: Network Performance Analysismethodology:1. Testing Commodity HardwareTo ensure that it is safe to use commodity 802.11x-based hardware to measure antenna patterns, we calibrate the sensitivity of our radios and analyze losses in the packet-based measurement platform. In the process of collection, some packets will be dropped due to interference or poor signal. In our experience, the percentage of dropped frames per angle is very small: the maximum lost frames per-angle in our datasets is on the order of 5%, with less than 1% lost being more common (the mean is 0.01675%).Moreover, the correlation coeffient between angle and loss percentage is -0.0451, suggesting that losses are uniformly distributed across angles. Given that we have taken 4000 samples in each direction (k=8 for our configuration), noise in our measurements due to packet loss is negligible.2. Experiment SettingWe collected data in several disparate environments with three different antennas.With the exception of the reference patterns, all of the measurements were made with commodity hardware by sending many measurement packets between two antennas and logging received signal strength (RSS) at the receiver. The three antenna configurations used include: - a HyperLink 24dBi parabolic dish with an 8-degree horizontal beam-width,- a HyperLink 14dBi patch with a 30 degree horizontal beam-width, and- a Fidelity Comtech Phocus 3000 8-element uniform circular phased array with a main-lobe beam-width of approximately 52 degrees.This phased array functions as a switched-beam antenna and can form this beam in one of 16 directions (on 22.5 degree increments around the azimuth). For the HyperLink antennas, we used the same antenna in all experiments to avoid intra-antenna variation due to manufacturing differences.In addition to the in-situ experiments, we have a “reference” data set for each configuration. The Array-Reference data set was provided to us by the antenna manufacturer. Because HyperLink could not provide us with data on their antennas, Parabolic-Reference and Patch-Reference were derived using an Agilent 89600S VSA and an Agilent E4438C VSG in a remote floodplain.3. ExperimentsFollowing is a brief description of each of the experiments:- Parabolic-Outdoor-A, Patch-Outdoor-A: A large open field on the University of X campus was used for these experiments. The field is roughly 500-feet on a side and is surrounded by brick buildings on two of the four sides. Although there is line of sight and little obstruction, the surrounding infrastructure makes this location most representative of an urban outdoor deployment.- Parabolic-Outdoor-B, Patch-Outdoor-B: A large University-owned floodplain on the edge of town was used for our most isolated data sets. The floodplain is flat, recessed, and is free from obstruction for nearly a quarter mile in all directions. This location is most representative of a rural backhaul link.- Array-Outdoor-A: The same open field is used as in the Parabolic-Outdoor-A and Patch-Outdoor-A data sets. The collection method here differs from that described in section 3. A single phased array antenna is placed approximately 100 feet away from an omni-directional transmitter. The transmitter sends a volley of packets from its fixed position as the phased array antenna electronically steers its antenna across each of its 16 states, spending 20 ms in each state. Several packets are received in each directional state. The phased array antenna is then manually rotated in 10 degree increments while the omni-directional emitter remains fixed. The same procedure is repeated for each of 36 increments. Moving the emitter changes not only the angle relative to the antenna but also the nodes’ positions relative to their environment.To address this confound, each physical position is treated as a separate experiment. This means that the number of angles relative to the steered antenna pattern is limited to the number of distinct antenna states (16). The tx-power of the radio attached to the directional antenna was turned down to 10dBm to produce more tractable noise effects (for the purpose of modeling small-scale behavior the default EIRP is much too high).- Parabolic-Indoor-A and Patch-Indoor-A: For this data set we used the University of X Systems Lab. The directional transmitter was positioned approximately 20 feet from the receiver in a walkway between cubicles and desks. This is our most cluttered environment.- Parabolic-Indoor-B, Parabolic-Indoor-C, Patch-Indoor-B, and Patch-Indoor-C: An indoor offce space was used for this set of tests. See figure 11 for the floor-floorplan of this office space. Two receivers were used here: one with line of sight and one without line of sight, placed amidst desks and offices.- Array-Indoor-A and Array-Indoor-B: Seven phased array antennas are deployed in the same 25x30m indoor office space used for Parabolic-Indoor-B, Parabolic-Indoor-C, Patch-Indoor-B, and Patch-Indoor-C. Data from two of the seven antennas are analyzed here. Each antenna electronically steers through its 16 directional states, spending 20 ms at each state. Two mobile omni-directional transmitters move through the space and transmit 500 packets at 44 distinct positions. For each packet received by a phased array, the packet’s transmission location and orientation is recorded (i.e., which of the four cardinal directions was the transmitter facing) along with the directional state in which the packet arrived and the RSSI value.- Parabolic-Reference and Patch-Reference: The large flood-plain is used here. An Agilent VSA is connected to the omni-directional receiver and makes a 10-second running average of power samples on a specific frequency (2.412 GHz was used). Three consecutive averages of both peak and band power are recorded for each direction. The directional transmitter is rotated in five degree increments and is connected to a VSG outputting a constant sinusoidal tone at 25 dBm on a specific frequency. Before, after, and between experiments we made noise floor measurements and as a post-processing step, we have subtracted the mean of this value (-59.61811 dBm or 0.0011 µW) from the measurements.4. NormalizationOur first task in comparing data sets is to come up with a scheme for normalization so that they can be compared to one another directly. For each data set, we find the mean peak value which is the maximum of the mean of samples for each discrete angle. This value is then subtracted from every value in the data set. The net effect is that the peak of the measurements in each data set will be shifted to zero.

本数据集为从2.4GHz定向天线（2.4 GHz directional antenna）采集的信号强度数据。我们采集信号强度数据旨在推导2.4GHz定向天线的参数化模型。
测量开始日期/时间：2007-08-16；测量结束日期/时间：2008-03-07

采集环境：随着无线网络需求的持续增长，学术界始终致力于探索提升网络性能的有效途径。其中一种提升网络吞吐量的方案是采用定向天线，以实现信号增益提升与干扰抑制。本次数据采集的核心目标正是推导2.4GHz定向天线的参数化模型。

网络配置：本次实验采用两台笔记本电脑，分别作为接收机与发射机。每台设备均搭载基于Atheros的MiniPCI-Express无线网卡，通过U.Fl转N尾纤适配器（U.Fl to N pigtail adapter）与一段LMR-400低损耗天线电缆连接至外置天线。接收机笔记本通过三脚架固定于距地面约2米处，搭载7dBi全向天线。发射机笔记本通过三脚架固定于距接收机100英尺处，同样距地面约2米，其所连接的正是本次待建模的定向天线。该发射三脚架搭载三轴齿轮转台，可实现高精度方位旋转。

数据采集方法：发射机无线网卡工作于802.11x ad-hoc模式（ad-hoc mode），使用当前最空闲的无线信道。手动修改发射机的ARP表（Address Resolution Protocol table），使其可向不存在的接收机地址发送UDP数据包。接收机工作于同信道的监听模式，通过tcpdump工具记录捕获的数据包。此外，需关闭接收机与发射机的天线分集功能。
设备部署完成后，具体采集流程如下：针对方位角上每5度的位置，发送500个未确认的UDP数据包。若无额外干预，由于MAC层（Media Access Control layer）重传机制，每个数据包都会被重传k次（k由无线网卡厂商及/或驱动实现决定），最终将产生k*500条有效测量数据。实验过程中，研究人员需注意远离天线的近场区域，且每次实验时需移动至同一位置，以避免自身成为环境中的静态干扰源。若需获取特定位置的额外数据，可使用多台接收机，但需对各接收机的数据分别处理——因为每条唯一的传输路径对应独特的传输环境。

局限性：本次研究未能及时获取电波暗室（anechoic chamber）用于实验，后续工作将考虑使用电波暗室以获取更纯净的参考测量数据。

轨迹集：信号强度轨迹集（signal strength traceset），即从2.4GHz定向天线采集的信号强度数据集合。
数据文件：cu-antenna-data-200905.tar.gz
数据集描述：我们采集信号强度数据旨在推导2.4GHz定向天线的参数化模型。
测量目的：网络性能分析（Network Performance Analysis）

实验方法：
1. 商用硬件测试
为验证使用商用802.11x系列硬件测量天线方向图的安全性，我们对无线网卡的灵敏度进行了校准，并分析了基于数据包的测量平台中的信号损耗。数据采集过程中，部分数据包会因干扰或信号不佳而丢失。根据我们的实验经验，每个角度的丢帧比例极低：数据集中单角度最大丢帧率约为5%，多数情况下丢帧率低于1%（平均值为0.01675%）。此外，角度与丢帧百分比的相关系数为-0.0451，表明丢帧在各个角度上的分布均匀。考虑到我们在每个方向上采集了4000个样本（本次配置下k=8），由数据包丢包带来的测量噪声可忽略不计。
2. 实验设置
我们在多种不同环境下使用三款不同的天线采集了数据。除参考方向图数据集外，所有测量均使用商用硬件完成：在两天线之间发送大量测量数据包，并在接收机端记录接收信号强度（Received Signal Strength, RSS）。本次实验使用的三款天线配置包括：
- HyperLink 24dBi抛物面天线，水平波束宽度（beam-width）为8度；
- HyperLink 14dBi贴片天线，水平波束宽度为30度；
- Fidelity Comtech Phocus 3000型8单元均匀圆形相控阵天线（phased array antenna），主波束宽度约为52度。
该相控阵天线属于切换波束天线，可在16个方位方向（方位角以22.5度为步进）形成波束。对于HyperLink系列天线，我们在所有实验中使用同一副天线，以避免因制造差异带来的天线内部不一致性。
除现场实验数据集外，我们还为每种天线配置获取了“参考”数据集。Array-Reference数据集由天线厂商提供。由于HyperLink无法为我们提供其天线的参考数据，Parabolic-Reference与Patch-Reference数据集通过安捷伦89600S矢量信号分析仪（Vector Signal Analyzer, VSA）与安捷伦E4438C矢量信号发生器（Vector Signal Generator, VSG）在远程河滩区域采集得到。
3. 实验详情
以下为各项实验的简要说明：
- Parabolic-Outdoor-A、Patch-Outdoor-A：本次实验在X大学校园内的一片大型开阔场地进行。该场地边长约500英尺，其四侧中有两侧被砖砌建筑环绕。尽管存在视距传输（line of sight）且遮挡极少，但周边建筑使得该场地最贴近城市户外部署场景。
- Parabolic-Outdoor-B、Patch-Outdoor-B：本次实验在市郊一片由校方所有的大型河滩区域进行，该区域是我们获取的最具隔离性的数据集。该河滩区域地势平坦、低洼，四周近四分之一英里范围内无任何遮挡，最贴近乡村回传链路（backhaul link）场景。
- Array-Outdoor-A：本次实验使用的场地与Parabolic-Outdoor-A及Patch-Outdoor-A一致，但采集方法与前文所述不同。将单台相控阵天线放置在距全向发射天线约100英尺处。发射天线固定位置，发送一批数据包，同时相控阵天线以电子方式切换至16个波束状态中的每一个，每个状态停留20毫秒。每个波束方向均可接收多个数据包。随后，手动将相控阵天线以10度为步进旋转，同时全向发射天线保持固定。上述流程针对36个旋转步进重复执行。移动发射天线不仅会改变天线相对的方位角，还会改变节点相对于周围环境的位置。为消除该混杂因素，每个物理位置均被视为独立实验。这意味着相对于相控阵天线波束方向图的可用角度数量，受限于天线的独立状态数（16个）。为便于建模小尺度行为（默认等效全向辐射功率（Equivalent Isotropically Radiated Power, EIRP）过高），我们将定向天线连接的无线网卡发射功率调低至10dBm，以得到更易处理的噪声影响。
- Parabolic-Indoor-A与Patch-Indoor-A：本次数据集采集于X大学系统实验室。定向发射天线与接收机之间的距离约为20英尺，部署在隔间与办公桌之间的走道中，是我们测试环境中最杂乱的场景。
- Parabolic-Indoor-B、Parabolic-Indoor-C、Patch-Indoor-B、Patch-Indoor-C：本次实验在一间室内办公区域进行。该办公区域的平面图详见图11。本次实验使用两台接收机：一台位于视距传输路径上，另一台位于办公桌与办公室之间，无直接视距。
- Array-Indoor-A与Array-Indoor-B：在与Parabolic-Indoor-B、Parabolic-Indoor-C、Patch-Indoor-B及Patch-Indoor-C相同的25×30米室内办公区域中，部署了7台相控阵天线。本次分析使用其中两台天线的数据。每台天线以电子方式切换16个波束方向，每个状态停留20毫秒。两台移动全向发射天线在该区域内移动，并在44个不同位置发送500个数据包。对于相控阵天线接收到的每个数据包，均会记录其传输位置、发射方向（即发射天线朝向的四个主方位），以及数据包到达时的天线波束状态与接收信号强度指示（Received Signal Strength Indicator, RSSI）值。
- Parabolic-Reference与Patch-Reference：本次实验使用前述大型河滩区域。将安捷伦VSA连接至全向接收机，对特定频率（本次使用2.412GHz）的功率采样进行10秒滑动平均。针对每个方位方向，记录三次连续的峰值功率与频带功率平均值。定向发射天线以5度为步进旋转，其连接的VSG以25dBm的功率输出特定频率的恒定正弦单音。实验前后及实验间隙，我们均进行了本底噪声（noise floor）测量；在后处理阶段，我们将所有测量值减去该本底噪声的平均值（-59.61811 dBm 或 0.0011 μW）。
4. 数据归一化
我们在不同数据集间进行对比的首要任务是制定归一化方案，以实现数据集间的直接对比。针对每个数据集，我们计算其平均峰值：即每个离散角度的样本平均值的最大值。随后，将该峰值从数据集中的所有数值中减去。最终效果为，每个数据集的测量峰值将被平移至零值点。