Non-orthogonal Multiple Access and Massive MIMO

Non-orthogonal Multiple Access and Massive MIMO Non-orthogonal Multiple Access and Massive MIMO for Improved Spectrum Efficiency To cope with the expected 1000x increase in mobile traffic over the next 10 years, key requirements are making more efficient use of the available frequency spectrum, increasing network speeds and opening-up more of the frequency spectrum for wireless applications. OFDMA used by LTE, etc., is being extended and superposition of signals for multiple users using a new power domain are being investigated as methods for increasing spectrum efficiency. In addition, high-directivity adaptive antennas with 100 or more elements offering good compatibility with higher frequencies, interference suppression, and simultaneous multi-user access are other potential ways to improve spectrum efficiency. This paper examines 5G wireless access systems and outlines non-orthogonal access and MIMO technologies along with some issues to resolve. 1 Introduction Next-generation 5G access systems are being investigated as a solution to the explosive increase (a factor of 1000x compared to 2010) in wireless data traffic forecast for the 2020s and the rapid appearance of various new. Three approaches are being taken towards supporting these huge traffic increases: making more efficient use of available frequencies, increasing network speeds, and opening-up new frequency bands. Making more efficient use of available frequencies is closely related to speeding-up the physical layer for multi-access and wireless access technologies. For example, increases of from 2.5 to 10 times have been proposed as targets for increasing the efficiency of 5G frequencies. Conventional mobile communications systems are moving towards faster digital wireless technologies based on advances in semiconductor devices as described below. The first generation (1G) used Frequency Division Multiple Access (FDMA), the second generation (2G) used Time Division Multiple Access (TDMA), the third generation (3G) is using Code Division Multiple Access (CDMA), and the 3.9G and fourth (4G) generations are using Orthogonal Frequency Division Multiple Access (OFDMA) supporting efficient frequency usage and good resistance to fading. The proposals for 5G systems aim to increase spectrum efficiency even further by speeding-up existing technologies, using newly opened frequency bands, and increasing network density, and support for the expected required conditions is being examined. The non-orthogonal multiple-access (NOMA) and higher-order multiple-input and multiple-output (MIMO) technologies described in this paper require huge processing power to implement these functio ns, which will be difficult to achieve using the performance of conventional semiconductor devices. Rapid developments in CPU processing power are expected to be a key element in deployment of 5G services. This paper describes the principles of each method related to these technologies and the problems to be resolved. 2 Non-orthogonal Multiple Access (NOMA) Multiple access is a basic function of cellular systems, which are usually divided into two types: orthogonal and non-orthogonal. In orthogonal access systems such as TDMA, FDMA, and OFDMA, signals for different users are orthogonal to each other. On the other hand, in non-orthogonal access systems, such as CDMA, TCMA (Trellis Coded Multiple Access), IDMA (Interleave Division Multiple Access), the cross-correlation of signals for different users is not 0. The commonly used NOMA incorporates the above-described non-orthogonal multiple access but this section discusses a specified NOMA implementation for 5G systems. NOMA under discussion for 5G systems has a new extension of the user multiplex domain to improve the spectrum efficiency. Intentionally introducing non-orthogonality aims to increase the spectrum efficiency further. As a result, technologies such as new encodings and an interference canceler are required to correct the non-orthogonality, which has been considered difficult to implement until now. However, development is pushing forward with the expectation of introduction as key 5G technology following recent remarkable improvements in CPU performance. NOMA can be classified into three different user multiplex domains: NOMA with SIC (Successive Interference Canceler)/SOMA (Semi-orthogonal Multiple Access), SCMA (Sparse Code Multiple Access), and IDMA (Interleave Division Multiple Access). In addition to the conventional frequency and time domains, these schemes aim to increase the spectrum efficiency by multiplexing the user in the power domain for NOMA with SIC/SOMA, in the power and code domains for SCMA, and in the code domain for IDMA. The follow sections explain the characteristics and principles of each of these schemes. 2.1 NOMA with SIC/SOMA NOMA with SIC (NOMA hereafter)/SOMA expands the radio resource allocation for the frequency and time domains used by LTE, etc. By superposing multiple user signals using the new power domain, it becomes possible to increase the spectrum efficiency even further and to increase the throughput. The NOMA and SOMA methods both make positive use of power and loss differences by modulation processing and multiplexing. Multiple users in the power domain are superposed at the symbol level. This method uses SIC, turbo code, and Low Density Parity Check Code (LDPC) at the receiver side to separate superposed users. The bit rate per 1 Hz for each user at this time (at superposition coding) is expressed by Eq. (1). User 2 with high channel gain is assigned the lower power P2 and the user with the low channel gain is assigned the higher power P1 to improve the average throughput for all users, resulting in improved spectrum efficiency. Figure 4 shows the throughput characteristics for both NOMA and Orthogonal Multiple Access (OMA) when there is a 20 dB difference in the receiver power levels; NOMA is characterized by an improvement of up to 2 bits/s/Hz compared to OMA. The difference between NOMA and SOMA is the symbol constellation. The post-superposition symbol constellation mappings are divided into NOMA with SIC without Gray- Mapping and SOMA with GrayMapping. Both methods are now being investigated in 3GPP Release13 RAN1 TSG as a Multi User Superposition Transmitter (MUST). For simplicity these methods are commonly both described as NOMA. 2.2 SCMA SCMA is a relatively new wireless multi-access method proposed in . It avoids the QAM symbol mapping used by conventional CDMA coding technologies and implements the binary data by coding it directly into multi-dimensional code words. Figure 5 shows the SCMA encoder block diagram. The figure shows a schematic of the SCMA encoder when there are four physical resources and four codewords in SCMA code book. Each user or layer assigns the binary data output from the FEC encoder directly to the complex codeword (physical resources dimensions) according to the predefined spreading code of the SCMA codebook. Additionally, multi-user connections are implemented by assigning a different unique code book to each user or layer. Table 2 shows an example of a codebook for six users or layers. As shown in Table 2, a message passing algorithm14) is used because the SCMA codebook contains sparse code words to achieve near-optimal detection of multiplexed data without increasing the complexity of pro cessing at the receiver side. 2.3 IDMA IDMA is a multi-access method first proposed and developed in 200015). It has gained popularity as one possible main access method for implementing the Internet of Things (IoT) and Machine to Machine (M2M) connections over 5G. In IoT/M2M communications, there are expected to be a large number of connected terminals sending small numbers of packets and instead of using packet scheduling based on OMA, the NOMA method is being considered be-cause it has good robustness to interference and does not require scheduling. IDMA within NOMA is known to have excellent user discrimination characteristics and a multi-user interference canceler can work effectively by combining an interleaver for each user with low-coding-rate error-correction coding to achieve a higher throughput com-pared to OFDMA. Additionally, IDMA is well suited to low-coding-rate error correction and is considered appropriate for transmitting the large number of multiplexed small-packet signals used by IoT, M2M, etc. After coding, the information bit sequence is rearranged by using a user-specific interleaved pattern to generate the encoded transmission bit sequence, which is mapped to the modulation symbols. The IDMA receiver is a parallel-type repeat multi-user receiver composed of a multi-user interference canceler and decoder. 2.4 Issues in Measurement Development As described so far, NOMA now under investigation for 5G has various methods. In particular, since the receiver performance depends directly on the SIC performance for NOMA, SOMA, and IDMA, measuring instruments must have functions for evaluating this performance correctly. However, there is presently no clear generation method for SCMA that includes codebook functions. Whether or not this can be solved either by standardization or by some implementation, development is pushing forward while watching trends in standardization and related technologies. 3.1 MIMO Evolution MIMO achieves high throughput and high reliability by using multiple antennas for transmitter and receiver (Figure 7) and it is a key technology in todays wireless communications systems. Furthermore, IEEE802.11ac and LTE-Advanced have adopted multi-user MIMO for simultaneous communications between base station with multiple antennas and multiple mobile terminals. Currently, Massive-MIMO is being proposed as a new technology for improving MIMO characteristics, targeting the 5G roll out. Massive-MIMO uses up-ward of 100 antenna elements to support simultaneous communications with multiple mobile terminals, greatly improving the spectrum usage efficiency. Figure 8: Massive-MIMO Configuration In addition, use of higher frequency bands, such as the millimeter-wave band is being investigated for 5G. Using the millimeter-wave band, is expected to support ultra-high-speed and large capacity communications using small cells, but transmission losses are big in the higher frequency bands and become bigger especially at non-line-of-sight communications (NLOS). Beam forming (BF) using Massive-MIMO antenna configurations (Figure 8) is thought to be effective in countering these increases in transmission losses. Since the antenna elements can be made small in proportion to the wavelength, the overall antenna size can be reduced even when using 100 or more antenna elements. Moreover, using Massive-MIMO can focus the energy to the mobile as a very tight beam, which not only improves the energy efficiency but is also expected to reduce interference between users. With 5G, in addition to conventional voice and internet services, video streaming, wireless Cloud, and M2M applications will become ubiquitous, requiring good service quality. In addition, these data communications will experience much higher variations in traffic levels with region and time, making it important to be able to accommodate bursts of user traffic in space and time. 3.2 Sub-Array Massive-MIMO In a Massive-MIMO configuration, a DAC is connected to each antenna element to form a digital BF configuration (Figure 9) supporting high-performance BF using digital signal processing. However, since the digital BF configuration requires a large number of high-speed DACs, the power consumption is extremely high. Moreover, using millimeter wave communications with the digital BF configuration widens the signal band, which requires high-speed signal processing. On the other hand, since analog BF using analog elements forms the same beam pattern in all bands, there is a risk that the received power of a user will drop when directing the beam at another user. Consequently, to lower the power consumption for millimeter-wave band communications, a hybrid method that can be implemented using smaller number of DACs has been proposed. This hybrid method combines both the analog and digital methods with send weighting to point beams simultaneously at multiple users; it achieves the same gain as digital BF using the massive configuration for all users. 3.3 Issues in Operation of Higher-Order MIMO Various factors including antenna design affect MIMO communication capacity. To be more precise, the following four factors are considered to cause MIMO communication capacity degradation. Inadequate selection of MIMO channel estimation algorithm Crosstalk between transmitter and receiver circuits MIMO gain reduction affected by Line of Sight (LOS) radio wave Inadequate antenna spacing and multiple reflections inside the housing Besides the above mentioned four points, in order to achieve further improvement of spectrum efficiency by using higher-order MIMO, the performances must be properly evaluated from the aspect of radio wave propagation, antenna and communication system. 4 Summary NOMA and MIMO are technologies for improving the spectrum efficiency for 5G wireless communications. The technologies have large benefits in terms of energy efficiency, spectrum efficiency, robustness, and reliability. Current base stations are both expensive and have poor efficiency at high power levels and there are proposals to replace them with massive combined modules featuring low cost and low power consumption. Achieving this requires solutions to various problems to maximize the potential of the technologies, such as complex antenna unit calculations, separation of analog and digital processing, synchronization of antenna units, etc. Additionally, implementing non-orthogonal access requires focus on increasing the power of devices for mobile terminals. Increasing the performance of semi-conductor devices offers a future chance to build high-speed digital signal processing such as SIC into more mobile terminals. Network Assisted Interference Cancellation and Suppression (NAICS ) using SIC is already being discussed by 3GPP for future introduction, and introduction of non-orthogonal access technologies such as NOMA is being proposed to ex-tend NAICS. Continuing active cooperation between industry and universities is required to solve the problems and assure future commercial roll outs. Anritsu has a wide range of measurement solutions for evaluating complex radio infrastructure and is continuing research in this field.

Qualitative Research Critique Essay

Hi, my name is Cindy Walters. I am presenting a qualitative research critique on a study conducted in 2011 on people with bipolar disorder with comorbid substance use. The study is entitled â€Å"The lived experience of adults with bipolar disorder and comorbid substance use disorder† written by Terry Ward, MSN, PhD, RN. Bipolar disorder involves changes in cognition, behavior, and mood. The episodes of bipolar disorder cycle through mania and depression. Mania is described as an elevated, irritable, or expansive mood, whereas depression is the opposite or hypomania. In the manic phase people present as euphoric, enthusiastic, and optimistic with an infectious personality. The euphoric state may suddenly may be replaced by extreme irritability if the persons needs are not met. In a manic phase the person’s speech may be rapid, loud, intrusive, and hard to follow or interrupt. If someone tries to interrupt a manic person he or she can just as quickly become, threatening, irritable or assaultive (Ebert, Loosen, Nurcombe & Leckman, 2008). Substance abuse is the excess use of drugs such as alcohol, illicit drugs, and prescription medications. The number of people abusing drugs and alcohol is about 3.4 million. Those individuals abusing have a greater change of acquiring a mental disorder at a rate of 2.7 times more likely than a non-abuser, according to the National Survey on Drug Use and Health individuals with a psychiatric diagnosis such as bipolar disorder have 28.8% chance of substance abuse or use of drugs. Individuals using drugs with a mental disorder, within a year are diagnosed as dependent on them (Ebert, Loosen, Nurcombe & Leckman, 2008). If bipolar disorder and substance use disorder are combined, they have a devastating effect with negative outcomes for those individuals. Understanding the problem with the ability to manage bipolar disorder with the proper treatment, health care providers can improve patient outcomes and his or her outlook on life. The problem is clearly stated in the abstract and first p aragraph of the study. Several statistics of drug use are quoted to give the reader an estimate and prevalence of this addiction with an unknown cause. The author addressed four hypotheses to explain this phenomenon. The negative outcomes in the use of substances and bipolar disorder affect a person mentally, physically, and functionally. The author stated the prevalence was high and does not receive enough attention in research studies. With increased knowledge, health care providers will be able to introduce new avenues for research, education, and nursing practice. The purpose of the study is to see how the individuals perceive their day- to- day experience of living with the disorders. A study done by Cassidy et al. (2001) addressed supporting and maintaining the patient’s stability and quality of life with effective treatment. Other studies focused on pharmacotherapy, psychosocial factors, and interventions as areas of research. Little research has been done on the phenomena. The researcher provided the broad platform for a qualitative study for individuals to share and speak freely of their experience with the hope the patients will be heard, get support, and have better outcomes. The method of this study was a descriptive and phenomenological design. â€Å"Phenomenology accepts that the truth can be revealed through the words of those that live the experience and that those words can describe the essence of that lived experience† (Thomas & Pollio, 2002, pg. 184). â€Å"Descriptive phenomenology has its emphasis on describing universal essences through direct interaction between the researcher and the objects of study† (Wojnar & Swanson, 2007, pg. 22). Conclusions could be drawn from the researcher of the subject experiences. The method adequately addressed the topic and gave credence to the subject experiences of living with a dual diagnosis. The design was consistent with qualitative studies and proved to be as descriptive and truthful as the researcher intended. Sampling was obtained over a four month period with the use of fliers. Fliers contained inclusion criteria and were validated by expert researchers for content, reliability, and readability. Also in the fliers contents were the researcher contact information, risks, and benefits of the study. Mental health care centers were the origin for the distribution of the fliers for subjects of the study. Snowballing and referrals came from doctor’s offices and recovery centers for abuse that were also included in the distribution of flier for subjects. The credibility came from phone calls made by potential subjects calling the researcher and were given reiterated instructions of the explanation for the study, inclusion criteria, exclusion criteria, risks, and benefits. The sample consisted of 12 stable subjects not using drugs with a self-reported bipolar disorders, and not currently manic or depressed. The demographics pulled out male, female, mean age, and nationality. The description of the inclusion criteria showed the participants inferred for the s ample were familiar and knowledgeable about the subject. The participants were chosen for the purpose of describing their experience of living with the dual diagnosis for this study. The criteria and descriptions were consistent for qualitative study. The sample size was small and consisted of only one male. Although facts indicate that more females have a dual diagnosis of bipolar disorder with substance use disorder (Ebert, Loosen, Nurcombe & Leckman, 2008). Data collection began with IRB approval and a written and verbal informed consent. Written consent was obtained for audiotaping of interviews with the understanding that at any time should the participant chose, the recorder could be turned off or the interview stopped. During emotional times of the participants they were asked by the researcher if they wanted the tape turned off or wish to stop the interview. Probe questions were used by the researcher to get the participant to expand on their explanations and thoughts. Wards probe questions were â€Å"describe for me a typical day that would help me understand what your life is like† or â€Å"how did you feel when you were told you had both bipolar disorder and a substance use disorder?† seemed to prompt the participant to speak (pg. 21). During the questions the researcher jotted notes on the mood, emotion, and expression of the participant the audio would not capture. Participants also shared concerns of ridicule, health problems that complicated their lives, and the lack of acceptance from society. There was no saturation of the data described. The strategy used by the researcher obtained the information she needed for the study. There were two interviews conducted the first was a face –to-face and the second was a follow up phone interview for clarity of the findings. The data collection was obtained in a qualita tive and purposeful manner, although the researcher never stated where the interview was conducted. There was no model or framework for validation of the study except for the data interpretation of the data analysis. Data analysis was studied over and over until the themes of the participants were identified by the researcher. Analytical coding was used to describe meaning to experiences lived by the participant. When a person reflects on their experience it becomes important to the process of understanding the phenomena. Qualitative methodology was proved with peer debriefing of the analysis and techniques used in this study. Audit trails comprised the data for the participants to view and verify that the disclosed information in his or her interview was captured as they intended that proved the validity and reliability of the research. Ward (pg. 22) found six themes that defined experiences of the participants. The six themes were life is hard, feeling the effect, trying to escape, spiritual support, being pushed beyond the limits, and a negative connotation. The participants res ponses were elaborated on in each theme giving the reader the implications of the perceptions of the participants. Each theme was explained and defined for easier reading and understanding. Themes indicated criminal actions, loss of jobs, homelessness, and losing the respect of others. Scientific rigor was not mentioned it could have been a useful tool. The participants lived and survived the experience they felt described as a sense of stigma, negative reactions from others, a sense of worthlessness, and a spiritual support that would help he or she feel as if there was someone they could talk to and as well as someone who would listen. The descriptions of the themes provided by the researcher gave one a visual of the feelings and emotions that a person with bipolar disorder with substance use disorder are trying to overcome on a day- to -day basis. The findings were concurrent with the way the participant felt about losing his or her ability to function in society. The diagnosis of bipolar disorder with substance use disorder kept challenges of coping and becoming productive in society at bay. Overcoming these obstacles proved to be a constant challenge. Without acceptance and forgiveness from society the need to overcome became more challenging and nonexistent. The participants had big dreams that were diminished by the disorders of bipolar and substance use creating havoc in their daily lives that he or she could not cope with. Health care workers can apply specific plans of care for mental health patients with individualized care plans on medication use and symptom management. Alternative plans can help patients find other ways of dealing with everyday problems than using drugs. Patients need education on medication compliance and screening for suicidal ideation. Concepts found in the themes of the study help organize the descriptions of the participants to reduce risk levels and incidence of harm. The type of data used is appropriate for a qualitative method of study. The conclusion of the study revealed and suggested being heard by others affected the participant’s feelings of self- worth and the need for help and support . Sharing with the reader the researcher makes society aware of the need for the voices of the participants to be heard. The individuals want to be heard, forgiven, and accepted by society. Increasing the awareness of mental health with nurses and the awareness of a higher power was a major accomplishment of this study. Indications for further research studies could provide healthcare workers with the tools needed to disrupt the stigma of mental illness and recognize when patients need help. Had the researcher given the benefits of this study to improving the effects of mental illness and the way society perceives it would have more benefit to the reader. This study was a good example of a qualitative study. Future studies require answers to more questions and a better and knowledgeable understanding of mental illness and substance use.

Hunger Games Book Report Essay

â€Å"The Hunger Games† is a the first book in a fantastic series of three books written by Suzanne Collins. It takes you into the life of a scared but quick-thinking, brave girl named Katniss Everdeen who learns how to survive on her own from a very young age when her father died in a mining accident. From that day on, she took care of her little family (mother and little sister, Prim) as well as herself by hunting in the woods of District 12 everyday with her guy friend Gale (who might have a thing for her but no one really knows). District 12 was one of the twelve districts that made up the country of Panem. Panem was once the continent of North America. When an epidemic swept through the continent of North America, Panem was formed and, the people who lived under the rules set by the capitol did not like it. They rebelled against the capitol and lost. Now, every year, children’s names, ages 12 through 18, are put into a bowl and drawn out during a ceremony known as â€Å"The Reaping. † This is a dreaded time and no one wants to be a part of it because they know that if their names are drawn, it is almost like a death sentence. When a name is called, you are then taken and thrown into what is known as â€Å"The Hunger Games. † Our narrator, main character, and hero also known as Katniss Everdeen, offered herself as a tribute in place of her younger sister Prim in an effort to save her life. When her and Peeta Mellark (the boy tribute from district 12) were taken off to the capitol, they went through some pretty intense training and in the end, well, you’ll have to read the book to find out what happened but it was sort of an unexpected ending. This book was so good because it kept you on your toes the whole time. I would rate it a solid 9. 5. I gave it that high of a rating because, the unexpected seemed to happen a lot and things popped up all the time out of no where. The book also kept a good pace and there weren’t to many dull moments; there was just enough detail that you could picture what was going on in your head while the story kept moving. The only thing that I did not like about this book was the fact that it seemed almost too futuristic. Yes, it is true that the story takes place millions of years from our present day but, it seemed almost to realistic. Crazy is a good word that describes what some of the people acted like that lived in the capitol. In all though, I really did think that this was a very good book and I would suggest it to anyone who was considering reading it.

Gang Violence During The 19th Century - 901 Words

 ¨Gang members have been responsible for 61 percent of all homicides [in Chicago] in 2011, up from 58.7 percent in 2010 ¨ (Hidden America). These are some of the few disturbing statistics about gang violence in Chicago; however, as many people do not know, gangs have not always been about drugs and violence. In the early 19th century, gangs are not what people perceive them to be today. Gangs in the 19th century were volunteers with the fire department back in the Antebellum Period, which is the period before the civil war and after the War of 1812. As time went on and as the professional firemen forced the volunteers to break up, they started spreading apart. Then by the late 19th century, gangs started developing on the south side. This is†¦show more content†¦As the years went by, and as white ethnic gangs began growing, white gangs started discriminating against other races, which would affect the remaining course of race relations. In 1869, male African Americans we re able to vote, which helped the Republicans advance in the elections. Therefore, white ethnic gangs started terrorizing the African Americans. The white ethnic gangs,  ¨[t]aking names like the Shielders and the Boundary Gang, white gangs patrolled the â€Å"color line† through the 1930s. These activities intensified with the accelerated migration of black southerners during World War II, prompting the Mayor s Commission on Human Relations in 1946 to establish a Juvenile Bureau to investigate the role of youth groups in anti-black violence ¨ (Diamond). As a defense against the racial violence, African Americans, Mexicans, and Puerto Ricans gangs rapidly increased all throughout the 1950s. The African American, Mexican, and Puerto Rican gangs made their marks around the city and have been known for taking over a neighborhood all throughout the 1960s. The Puerto Rican gangs resided in Humboldt Park; the Mexican gang brimmed Pilson and 18th street, and the African American gangs stayed by the South and West sides. Many of the people who join gangs are very young, ranging