nist/multihop2007082036200708202007-11-15nist/multihopDataset of experiments for the automated deployment of a multihop wireless network.To assess the feasibility of deploying wireless relays in real
time, we conducted a series of experiments using 900 MHz
TinyOS Crossbow MICA2 Motes (MPR400CB).the initial version2007-08-202005-12-012006-11-30souryal-multihop139140141142143http://www.antd.nist.gov/~souryal/#pubhttp://www.crawdad.org/wiki/pmwiki.php?n=Main.Dataset.nist-multihopsensor networksignal strengthwireless multihop networksNetwork Performance AnalysisRouting Protocolsensor networkWhen the range of single-hop wireless communication is limited
by distance or harsh radio propagation conditions, relays
can be used to extend the communication range through
multihop relaying.
To assess the feasibility of deploying wireless relays in real
time, we conducted a series of experiments using 900 MHz
TinyOS Crossbow MICA2 Motes (MPR400CB).A prototype system is implemented based on 900 MHz TinyOS motes
supporting low-speed data applications including text messaging,
sensor data and Radio Frequency Identification (RFID)-assisted
localization.Please see <configuration> section of each trace for the collection methodology of each experiment.50200708202007-11-15the initial version.nist/multihop/experimentsTraceset of experiments for the automated deployment of a multihop wireless network.To assess the feasibility of deploying wireless relays in real
time, we conducted a series of experiments using 900 MHz
TinyOS Crossbow MICA2 Motes (MPR400CB).2007-08-202005-12-012006-11-30139140141142143Network Performance AnalysisRouting ProtocolTo assess the feasibility of deploying wireless relays in real
time, we conducted the following experiments using 900 MHz
TinyOS Crossbow MICA2 Motes (MPR400CB).
- RSS-based Link Assessment
The purpose of the first experiment was to determine whether
the received signal strength (RSS) measurement of the motes
is a useful predictor of link quality and, if so, to characterize
the relationship between link reliability and RSS. Results were
collected using a layout of 12 transmitter locations and 10 receiver
locations on a single floor of an office building. The layout is
shown in [Figure: Layout] (Layout for RSS-based link assessment experiment),
where transmitter locations are triangles and receiver locations are stars.
The result of this experiment is shown in
[Figure: success rate vs. RSS] (Packet success rate vs. received signal strength),
which plots the percentage of correctly decoded packets as a function of
the average RSS (one data point for each batch received by a mote).
- Temporal Variability of a Mobile Link
We measured RSS from a mobile receiver to gain an appreciation for
the extent of fluctuations of RSS at pedestrian speeds in a typical
building environment,
The result of this experiment is shown in
[Figure: RSS vs. time] (Received signal strength vs. time at a mobile receiver),
which plots the measured RSS as a function of time.
- Receiver Height
We measured RSS from receivers positioned at different heights,
with a fixed transimitter positioned at 38 cm above the floor.
The motivation of this experiment is that a practical consideration
in many applications of realtime relay deployment is the effect
of a receiver's height on the quality of the link.
For example, if the transceiver monitoring link quality is positioned
at a given height, we wish to know if there is a consistent degradation
in link quality if the new relay is deployed at a different height,
say on the floor. A scenario of this type might be a first responder
with a monitoring radio strapped to his/her belt along with a canister
ejecting relays onto the floor as needed.
The result of this experiment is shown in
[Figure: RSS vs. receiver height]
(Received signal strength vs. tx-rx distance and receiver height),
which plots the average RSS as a function of transmitter-receiver
distance for each of the three receiver heights. The first six distance
measurements were made with line-of-sight (LOS) links, while the last two
(beyond 23 m) were non-LOS.
- Link Symmetry
To test RSS symmetry, we compared the RSS measured
at each end of a fixed point-to-point link.
The result of this experiment is shown in
[Figure: Link Symmetry],
(Instantaneous received signal strength of received packets and acknowledgments),
which plots the instantaneous RSS measurements made on receipt
of the packets and the ACKs for both links over a total duration
of 250 s.
- Parameter Selection for the relay deployment algorithm in [soryal-multihop]
(See Section 5 in [souryal-multihop] for details of the relay deployment algorithm.)
Implementation of the deployment algorithm requires selecting values
for parameters including the probe period (D), the RSS averaging
filter length (N), and the threshold for triggering deployment (Sth).
Values for the probe period D and averaging filter length N were selected
after studying the performance of the algorithm for different (D, N) pairs.
The product D*N represents the duration of the observation window over
which the RSS average is computed.
1. Selection of the probe period
[Figure: Selection of probe period D]
(Deviation from deployment threshold for three different choices of probe period D and RSS filter length N)
shows the results of four separate trials for each of three pairs
of (D, N). The trials consisted of two different paths, and two trials of
each path. Results are given in terms of the difference between the
steady-state RSS and the deployment threshold, chosen here to be Sth = -80 dBm.
2. Selection of the RSS filter length
We then examined different choices of the RSS filter length, N.
[Figure: Selection of the RSS filter length N]
(Figure: Deviation from deployment threshold vs. RSS filter length N; probe period D = 100 ms)
illustrates results of trials for four different values of N and
a fixed probe period of D = 100ms.
3. Validation
The choices of N = 20 and D = 100ms appears to strike a balance
between consistency and latency.
Five additional trials of this choice of parameters were done,
and the results are shown in
[Figure: Validation]
(Deviation from deployment threshold with probe period D = 100 ms and RSS filter length N = 20).
- Experimental Trials
The prototype for real-time network deployment was tested
in the eleven-story Administration building on the main
campus of the National Institute of Standards and Technology.
In each trial, the base node was located in the ground floor
lobby. The mobile node was started next to the base, was walked
to a stairwell and then up to the top floor, with relays
being placed on the floor when indicated by the deployment
algorithm [souryal-multihop]. After stopping at the top for
data collection, the mobile node was then walked down the
same path to the base node on the ground floor, passing the
relays that were deployed on the way up.
In most cases, we were able to reach the 10th or 11th floor
with 9 deployed relays. Typically, 2 relays were deployed
between the base node and the stairwell door, and the remainder
were deployed inside the stairwell, roughly one relay per 1 1/2
floors.
During the deployment phase, the stop phase, and the
return phase, message traffic was automatically generated
by the base node application to measure delivery rates and
round-trip delays. Specifically, a ping-like message was sent
every 4 s to the mobile node's mote, which sent a reply to
the base. While at the top of the building, the base node
application also sent automatically generated text messages
every 4 s to the peer application on the mobile node's PDA.
The PDA logged each message that was received and replied
to it with a text message. Round-trip delay and delivery
rate were measured from the ping messages, and one-way
delivery rates were measured from the auto-text messages.
The result of this experiment is shown in
[Figure: Prototype] (Ping roundtrip delay vs. time of trial 3),
which plots ping roundtrip delay over the course of trial 3./download/nist/multihop/souryal_mobisys2007_data.tar.gz/download/nist/multihop/souryal_mobisys2007_figs/layout.png/download/nist/multihop/souryal_mobisys2007_figs/rss_success-rate.png/download/nist/multihop/souryal_mobisys2007_figs/time_rss.png/download/nist/multihop/souryal_mobisys2007_figs/receiver-height.png/download/nist/multihop/souryal_mobisys2007_figs/link_symmetry.png/download/nist/multihop/souryal_mobisys2007_figs/selection-D.png/download/nist/multihop/souryal_mobisys2007_figs/selection-N.png/download/nist/multihop/souryal_mobisys2007_figs/validation.png/download/nist/multihop/souryal_mobisys2007_figs/prototype.pngnist/multihop129200708202007-11-15the initial versionnist/multihop/experiments/rss_success-rateTrace of RSS-based link assessment for the automated deployment of a multihop wireless network.Trace of RSS-based link assessment for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30143141140At each transmitter location, a batch of 200 packets was transmitted,
and the receivers recorded the sequence number, CRC result and RSS
(in dBm) of each detected packet. The transmitter repeated the transmission
batch at six different transmission power levels, (-20, -15, -10, -5, 0 and 5)
dBm, in order to obtain a finer range of RSS data points.
The result of this experiment is shown in
[Figure: Packet success rate vs. received signal strength], which
plots the percentage of correctly decoded packets as a function of
the average RSS (one data point for each batch received by a mote).The file "rss_success-rate.txt" consists of:
- first column: avg rss (dBm)
- second column: pkt succ rate/download/nist/multihop/souryal_mobisys2007_figs/rss_success-rate.pngnist/multihop/experiments130200708202007-11-15the initial versionnist/multihop/experiments/time_rssTrace of RSS measurement with a mobile receiver for the automated deployment of a multihop wireless network.Trace of RSS measurement with a mobile receiver for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139We placed a receiver on a small vehicle moving down an office
corridor away from a fixed transmitter at a speed of approximately
0.3 m/s. The total distance covered was 20 m.
Packets were transmitted at a rate of 50 packets/s, and the
mobile receiver recorded the RSS of each detected packet.
The result of this experiment is shown in
[Figure: Received signal strength vs. time at a mobile receiver],
which plots the measured RSS as a function of time.The file "time_rss.txt" consists of:
- first column: time (sec)
- second column: rss (dBm)/download/nist/multihop/souryal_mobisys2007_figs/time_rss.pngnist/multihop/experiments131200708202007-11-15the initial versionnist/multihop/experiments/receiver-heightTrace of RSS measurement with different receiver heights for the automated deployment of a multihop wireless network.Trace of RSS measurement with different receiver heights for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139A fixed transmitter positioned at 38 cm above the floor
of an office corridor transmitted packets to a fixed receiver
positioned at one of three heights above the floor: 120 cm,
38 cm, and directly on the floor. The experiment was repeated
at several transmitter-receiver separation distances.
At each distance and height, 250 packets were transmitted,
and the receiver logged the RSS of each detected packet.
The result of this experiment is shown in
[Figure 4: Received signal strength vs. tx-rx distance and receiver height],
which plots the average RSS as a function of transmitter-receiver
distance for each of the three receiver heights. The first six distance
measurements were made with line-of-sight (LOS) links, while the last two
(beyond 23 m) were non-LOS.The file "receiver-height.txt" consists of:
- first column: tx-rx dist (m)
- second column: average rss of a receiver at 120 cm high (dBm)
- third column: average rss of a receiver at 38 cm high (dBm)
- fourth column: average rss of a receiver at on floor (dBm)/download/nist/multihop/souryal_mobisys2007_figs/receiver-height.pngnist/multihop/experiments132200708202007-11-15the initial versionnist/multihop/experiments/link-symmetryTrace of RSS measurement in bidirectional link for the automated deployment of a multihop wireless network.Trace of RSS measurement in bidirectional link for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139One transceiver transmitted 1000 packets at a rate of 4 packets/s,
and the other transceiver immediately replied with an acknowledgment
(ACK) for each packet it successfully received using the built-in
ACK of theMAC. The second transceiver recorded the RSS of each packet
it detected, while the first transceiver recorded the RSS of each ACK
it detected.
In this way, we were able to make nearly simultaneous measurements
of the RSS in both directions of the link. Measurements were taken
for a relatively strong link (approximately 2 m, LOS) and a second
link roughly 20 dB weaker (approximately 7 m, non-LOS). Using a spectrum
analyzer, we observed no other emissions on the same 900 MHz channel
(i.e., an interference-free environment).
To test RSS symmetry, we compared the RSS measured
at each end of a fixed point-to-point link.
The result of this experiment is shown in
[Figure: Instantaneous received signal strength of received packets and acknowledgments],
which plots the instantaneous RSS measurements made on receipt
of the packets and the ACKs for both links over a total duration
of 250 s.The file "link-symmetry.txt" consists of:
- first column: packet no.
- second column: rss of Link 1 Packet (dBm)
- third column: rss of Link 1 ACK (dBm)
- fourth column: rss of Link 2 Packet (dBm)
- fifth column: rss of Link 2 ACK (dBm)/download/nist/multihop/souryal_mobisys2007_figs/link_symmetry.pngnist/multihop/experiments133200708202007-11-15the initial versionnist/multihop/experiments/selection-DTrace of an experiment for parameter selection for the automated deployment of a multihop wireless network.Trace of an experiment for parameter selection for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139To implement the deployment algorithm requires, we tried to select values
for parameters including the probe period (D), the RSS averaging
filter length (N), and the threshold for triggering deployment (Sth).
We tested values for (D, N) corresponding to a fixed observation window
of D = 4 seconds. For each trial, the measuring node executing the
real-time link assessment algorithm (Section 4 in [souryal-multihop])
was carried away from a fixed relay in an office building environment
at walking speed. When the measuring node gave the indication to deploy,
the node was placed on the floor and a long sequence of packet transmissions
was initiated over the fixed link to measure the steady-state RSS.
The result for selecting the probe period (D) is shown in
[Figure: Deviation from deployment threshold for three different choices of probe period D and RSS filter length N].
The plot shows the results of four separate trials for each of three pairs
of (D, N). The trials consisted of two different paths, and two trials of
each path. Results are given in terms of the difference between the
steady-state RSS and the deployment threshold, chosen here to be Sth = -80 dBm.The file "selection-D.txt" consists of:
- first column: RSS-Sth with Delt=100 N=40 (dB)
- second column: RSS-Sth with Delt=200, N=20 (dB)
- third column: RSS-Sth with Delt=500, N=8 (dB)/download/nist/multihop/souryal_mobisys2007_figs/selection-D.pngnist/multihop/experiments134200708202007-11-15the initial versionnist/multihop/experiments/selection-NTrace of an experiment for parameter selection for the automated deployment of a multihop wireless network.Trace of an experiment for parameter selection for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139To implement the deployment algorithm requires, we tried to select values
for parameters including the probe period (D), the RSS averaging
filter length (N), and the threshold for triggering deployment (Sth).
We tested values for (D, N) corresponding to a fixed observation window
of D = 4 seconds. For each trial, the measuring node executing the
real-time link assessment algorithm (Section 4 in [souryal-multihop])
was carried away from a fixed relay in an office building environment
at walking speed. When the measuring node gave the indication to deploy,
the node was placed on the floor and a long sequence of packet transmissions
was initiated over the fixed link to measure the steady-state RSS.
The result for selecting the averaging filter length (N) is shown in
[Figure: Deviation from deployment threshold vs. RSS filter length N; probe period D = 100 ms].
The plot shows the results of trials for four different values of N and
a fixed probe period of D = 100ms.The file "selection-N.txt" consists of:
- first column: RSS-Sth with Delt=100 N=5 (dB)
- second column: RSS-Sth with Delt=100, N=10 (dB)
- third column: RSS-Sth with Delt=100, N=20 (dB)
- fourth column: RSS-Sth with Delt=100, N=40 (dB)/download/nist/multihop/souryal_mobisys2007_figs/selection-N.pngnist/multihop/experiments135200708202007-11-15the initial versionnist/multihop/experiments/validationTrace of an experiment for parameter selection for the automated deployment of a multihop wireless network.Trace of an experiment for parameter selection for the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30140139To implement the deployment algorithm requires, we tried to select values
for parameters including the probe period (D), the RSS averaging
filter length (N), and the threshold for triggering deployment (Sth).
We tested values for (D, N) corresponding to a fixed observation window
of D = 4 seconds. For each trial, the measuring node executing the
real-time link assessment algorithm (Section 4 in [souryal-multihop])
was carried away from a fixed relay in an office building environment
at walking speed. When the measuring node gave the indication to deploy,
the node was placed on the floor and a long sequence of packet transmissions
was initiated over the fixed link to measure the steady-state RSS.
The choices of N = 20 and D = 100ms appears to strike a balance
between consistency and latency. Five additional trials of this choice
of parameters were done, and the results are shown in
[Figure: Deviation from deployment threshold with probe period D = 100 ms and RSS filter length N = 20].The file "validation.txt" consists of:
- first column: RSS-Sth with Delt=100 N=20 (dB)/download/nist/multihop/souryal_mobisys2007_figs/validation.pngnist/multihop/experiments136200708202007-11-15the initial versionnist/multihop/experiments/prototypeTrace of experimental trials with the prototype of the automated deployment of a multihop wireless network.Trace of experimental trials with the prototype of the automated deployment of a multihop wireless network.false2007-08-202005-12-012006-11-30142139The prototype for real-time network deployment was tested
in the eleven-story Administration building on the main
campus of the National Institute of Standards and Technology.
In each trial, the base node was located in the ground floor
lobby. The mobile node was started next to the base, was walked
to a stairwell and then up to the top floor, with relays
being placed on the floor when indicated by the deployment
algorithm [souryal-multihop]. After stopping at the top for
data collection, the mobile node was then walked down the
same path to the base node on the ground floor, passing the
relays that were deployed on the way up.
In most cases, we were able to reach the 10th or 11th floor
with 9 deployed relays. Typically, 2 relays were deployed
between the base node and the stairwell door, and the remainder
were deployed inside the stairwell, roughly one relay per 1 1/2
floors.
During the deployment phase, the stop phase, and the
return phase, message traffic was automatically generated
by the base node application to measure delivery rates and
round-trip delays. Specifically, a ping-like message was sent
every 4 s to the mobile node's mote, which sent a reply to
the base. While at the top of the building, the base node
application also sent automatically generated text messages
every 4 s to the peer application on the mobile node's PDA.
The PDA logged each message that was received and replied
to it with a text message. Round-trip delay and delivery
rate were measured from the ping messages, and one-way
delivery rates were measured from the auto-text messages.
The result of this experiment is shown in
[Figure: Ping roundtrip delay vs. time of trial 3],
which plots ping roundtrip delay over the course of trial 3.The file "prototype.txt" consists of:
- first column: time (s)
- second column: roundtrip time (s)/download/nist/multihop/souryal_mobisys2007_figs/prototype.pngnist/multihop/experiments139nist/multihopMichael R. Souryalsouryal@nist.govNational Institute of Standards and TechnologyWireless Communication Technologies GroupElectronics Engineer100 Bureau Drive, Mail Stop 8920, Gaithersburg, MD 20899-8920(301) 975-4342(301) 975-6238http://www.antd.nist.gov/~souryal/140nist/multihopJohannes Geissbuehlerhannes.geissbuehler@gmail.com,AdNovumAdNovum, Zurich, Switzerland.141nist/multihopKamran Sayrafian-Poursayrafia@nist.govNational Institute of Standards and Technology142nist/multihopAndreas Wapfandreas.wapf@nist.govNational Institute of Standards and Technology143nist/multihopJulio PerezNational Institute of Standards and Technologysouryal-multihopMichael R. SouryalJohannes GeissbuehlerLeonard E. MillerNader MoayeriReal-time deployment of multihop relays for range extensionMobiSys '07: Proceedings of the 5th international conference on Mobile systems, applications and services2007--06--85-98San Juan, Puerto Ricohttp://doi.acm.org/10.1145/1247660.1247673http://doi.acm.org/10.1145/1247660.1247673ACM PressDeployment, multihop wireless networks, first responders, breadcrumbs, sensors, RFIDWhen the range of single-hop wireless communication is limited by distance or
harsh radio propagation conditions, relays can be used to extend the
communication range through multihop relaying. This paper targets the need in
certain scenarios for rapid deployment of these relays when little or nothing
is known in advance about a given environment and its propagation
characteristics. Applications include first responders entering a large
building during an emergency, search and rescue robots maneuvering a disaster
sight, and coal miners working underground. The common element motivating this
work is the need to maintain communications in an environment where single-hop
communication is typically inadequate. This paper investigates the feasibility
of the automated deployment of a multihop network. A deployment procedure is
proposed that employs real-time link measurements and takes into account the
physical layer characteristics of a mobile multipath fading environment and the
radio in use. A prototype system is implemented based on 900 MHz TinyOS motes
supporting low-speed data applications including text messaging, sensor data
and Radio Frequency Identification (RFID)-assisted localization. Results of
deployments in a hi-rise office building are presented.measurementwirelessnist_multihopcrawdadnist/multihop20070601